Impax Asset Management Group, a UK-based asset manager focused on sustainable investing, has agreed to acquire US rival Pax World Management.

Impax will initially pay $52.5m for the deal, which is subject to shareholder approval. The firm will also make additional contingent payments of up to $37.5m in 2021 depending on the performance of Pax, which provides equity and fixed income strategies and manages £3.47bn in assets.

The combined entity will manage £10.3bn in assets, with both companies to retain their existing management and investment teams.

Pax will be rebranded as Impax Investment Management (US) following the acquisition, though mutual funds managed by Pax will continue to operate under the Pax brand.

Pax president and CEO Joe Keefe will continue to spearhead the new entity and will also join the Impax board.

Impax and Pax have been working together for a decade in the management of the Pax Global Environmental Markets Fund that managed $511m in assets at the end of August 2017.

Impax founder and CEO Ian Simm said: “Like Impax, Pax has a long track record as a pioneer in sustainable investing and a strong team of highly experienced investment management and support staff.  The combined group will start with a closely aligned business culture and be well placed to offer a broader service and more diversified range of products to existing and future clients.”