Business Combination Prospectus (Form 425)

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or Section 15(d) of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): December 19, 2025

PLUM ACQUISITION CORP. IV

(Exact name of registrant as specified in its charter)

Cayman Islands		001-42472		98-1795710
(State or other jurisdiction of incorporation or organization)		(Commission File Number)		(I.R.S. Employer Identification Number)

2021 Fillmore St. #2089 San Francisco, California		94115
(Address of principal executive offices)		(Zip Code)

Registrant's telephone number, including area code: (929) 529-7125

Not Applicable

(Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation to the registrant under any of the following provisions:

☒	Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)
☐	Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)
☐	Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))
☐	Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Title of each class		Trading Symbol(s)		Name of each exchange on which registered
Units, each consisting of one Class A ordinary share, par value $0.0001 per share, and one-half of one redeemable warrant		PLMKU		Nasdaq Global Market
Class A ordinary shares, par value $0.0001 per share, included as part of the units		PLMK		Nasdaq Global Market
Warrants included as part of the units, each whole warrant exercisable for one Class A ordinary share at an exercise price of $11.50		PLMKW		Nasdaq Global Market

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 or Rule 12b-2 of the Securities Exchange Act of 1934.

Emerging growth company ☒

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Item 7.01. Regulation FD Disclosure.

On December 19, 2025, Plum Acquisition Corp. IV, a special purpose acquisition company (the "Company"), and American Critical Resources ("ACR"), a subsidiary of Controlled Thermal Resources Holdings Inc. ("CTR"), issued a press release announcing that they have entered into a non-binding letter of intent for a potential business combination. A copy of the press release is attached as Exhibit 99.1 hereto and incorporated by reference herein.

No assurances can be made that the Company and ACR will successfully negotiate and enter into a definitive agreement, or that the proposed business combination will be consummated on the terms currently contemplated, or at all. Any transaction would be subject to the completion of due diligence, the negotiation of a definitive agreement providing for the proposed business combination, satisfaction of the conditions negotiated therein, board and equity holder approval, regulatory approvals, and other customary conditions.

The information in this Item 7.01, including Exhibit 99.1, is furnished and shall not be deemed "filed" for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the "Exchange Act"), or otherwise subject to liabilities under that section, and shall not be deemed to be incorporated by reference into the filings of the Company under the Securities Act of 1933, as amended, or the Exchange Act, regardless of any general incorporation language in such filings.

Additional Information and Where to Find It

If a definitive agreement is entered into in connection with the proposed business combination, the Company or a newly formed holding company will prepare a registration statement on Form S-4, which will include a preliminary proxy statement of the Company containing information about the proposed business combination and the respective businesses of the Company and ACR, as well as the prospectus relating to a potential newly formed holding company's securities to be issued in connection with the completion of the proposed business combination, to be filed with the U.S. Securities and Exchange Commission ("SEC"). In an instance where a definitive agreement is executed and after the registration statement is declared effective, the proxy statement/prospectus will be mailed to the Company's shareholders. The Company urges investors and other interested persons to read, when available, the proxy statement/prospectus, as well as other documents filed with the SEC, because these documents will contain important information about the proposed business combination. Such persons can also read the Company's reports filed with the SEC for a description of the security holdings of its officers and directors and their respective interests as security holders in the consummation of the proposed transactions described herein. The proxy statement/prospectus, once available, and the Company's reports can be obtained, without charge, at the SEC's website (http://www.sec.gov) or by directing a request to: Plum Acquisition Corp. IV, 2021 Fillmore St., #2089, San Francisco, California 94115, Attention: Kanishka Roy, or by email at [email protected].

Participants in the Solicitation

The Company or a newly formed holding company, ACR and their respective directors, executive officers and other members of their management and employees, under SEC rules, may be deemed to be participants in the solicitation of proxies of the Company's shareholders in connection with the proposed business combination. Investors and security holders may obtain more detailed information regarding the names, affiliations and interests of the Company's directors and officers in the Company's reports filed with the SEC. Information regarding the persons who may, under SEC rules, be deemed participants in the solicitation of proxies to the Company's shareholders in connection with the proposed business combination will be set forth in the proxy statement/prospectus for the proposed business combination when available. Information concerning the interests of ACR and the Company's participants in the solicitation, which may, in some cases, be different than those of their respective equityholders generally, will be set forth in the proxy statement/prospectus relating to the proposed business combination when it becomes available.

Forward-Looking Statements:

This Current Report on Form 8-K and the exhibit hereto include "forward-looking statements" with respect to the Company and ACR. All information in this press release concerning ACR has been provided solely by ACR and has not been independently verified by the Company, which makes no representation or warranty as to the accuracy or completeness of such information and assumes no obligation to update the information in this press release, except as required by law. The expectations, estimates, and projections of the businesses of ACR and the Company may differ from their actual results and consequently, you should not rely on these forward-looking statements as predictions of future events. Words such as "expect," "estimate," "project," "budget," "forecast," "anticipate," "intend," "plan," "may," "will," "could," "should," "believes," "predicts," "potential," "continue," and similar expressions are intended to identify such forward-looking statements. These forward-looking statements include, without limitation, expectations with respect to the execution and delivery of a definitive agreement with respect to the proposed business combination, expectations with respect to future performance and anticipated financial impacts of the proposed business combination, the satisfaction of the closing conditions to the proposed business combination, and the timing of the completion of the proposed business combination. These forward-looking statements involve significant risks and uncertainties that could cause the actual results to differ materially from the expected results. Most of these factors are outside of the control of ACR and the Company and are difficult to predict. Factors that may cause such differences include, but are not limited to: (1) the occurrence of any event, change or other circumstances that could give rise to the termination of the negotiations and any subsequent definitive agreements with respect to the proposed business combination, and the possibility that the terms and conditions set forth in any definitive agreements with respect to the proposed business combination may differ materially from the terms and conditions set forth in the letter of intent; (2) the outcome of any legal proceeding that is ongoing or may be instituted against the parties following the announcement of the proposed business combination and any definitive agreements with respect thereto; (3) the inability to complete the proposed business combination, including due to failure to obtain approval of the shareholders of ACR and the Company or other conditions to closing; (4) the inability to obtain or maintain the listing of the post-acquisition company's securities on the Nasdaq Stock Market LLC, the New York Stock Exchange, or another national securities exchange following the proposed business combination; (5) the risk that the proposed business combination disrupts current plans and operations as a result of the announcement and consummation of the proposed business combination; (6) the ability to recognize the anticipated benefits of the proposed business combination, which may be affected by, among other things, competition, the ability of the combined company to grow and manage growth profitably and retain its key employees; (7) costs related to the proposed business combination; (8) changes in applicable laws or regulations; and (9) risks related to ACR's business, including fluctuations in demand and prices for lithium and other critical minerals, competition within the industry, the risks inherent in development projects and exploration activities, potential delays or cost overruns in capital expenditures, the ability to secure necessary raw materials, compliance with regulatory requirements, environmental and safety obligations, economic and market conditions, and political or geopolitical developments; (10) the "Risk Factors" sections of the most recent Annual Report on Form 10-K filed with the SEC by the Company; other risks and uncertainties included in documents filed or to be filed with the SEC by ACR and the Company. The foregoing list of factors is not exclusive. You should not place undue reliance upon any forward-looking statements, which speak only as of the date made. ACR and the Company do not undertake or accept any obligation or undertaking to release publicly any updates or revisions to any forward-looking statements to reflect any change in their expectations or any change in events, conditions, or circumstances on which any such statement is based, except as required by law. Past performance by ACR's or the Company's management teams and their respective affiliates is not a guarantee of future performance. Therefore, you should not place undue reliance on the historical record of the performance of ACR's or the Company's management teams or businesses associated with them as indicative of future performance of an investment or the returns that ACR or the Company will, or are likely to, generate going forward.

No Offer or Solicitation

This Current Report on Form 8-K and the exhibit hereto shall not constitute a solicitation of a proxy, consent, or authorization with respect to any securities or in respect of the proposed business combination. This Current Report on Form 8-K and the exhibit hereto shall also not constitute an offer to subscribe for, buy or sell or an invitation to subscribe for, buy or sell any securities or the solicitation of any vote or approval in any jurisdiction pursuant to or in connection with the proposed business combinations or otherwise, nor shall there be any sale of securities in any states or jurisdictions in which such offer, solicitation, or sale would be unlawful prior to registration or qualification under the securities laws of any such jurisdiction.

Item 9.01. Financial Statements and Exhibits.

(c) Exhibits.

Exhibit No.		Description
99.1		Press release dated December 19, 2025
104		Cover Page Interactive Data File (embedded within the Inline XBRL document)

SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

Date: December 19, 2025	PLUM ACQUISITION CORP. IV
	By:	/s/ Kanishka Roy
	Name:	Kanishka Roy
	Title:	Chief Executive Officer