Houston-based private equity firm Ara Partners has purchased Germany’s Vacuumschmelze (VAC), a producer of magnetic materials for products such as electric vehicles, from funds overseen by asset manager Apollo. The purchase price wasn’t disclosed.

VAC is the only producer in the Western Hemisphere of electric-vehicle-grade permanent magnets. It also makes magnetic materials for the industrial, aerospace, medical, and renewable energy sectors.

Earlier this year, VAC announced a deal with automotive giant General Motors to build a North American factory for the production of magnets for the electric motors of GM-made EVs. The factory, set to open in 2025, will initially product enough magnets to supply 1 million EVs each year. The magnets will be made of alloys of rare-earth elements.

GM forecasts it will manufacture 1 million EVs per year in North America by 2025.

“We believe the demand for VAC’s differentiated, customized products will continue to grow rapidly as companies around the world decarbonize their industrial processes and the electrification of mobility advances, and we look forward to leveraging our expertise to further enable VAC’s continued success,” Tuan Tran, a partner at Ara Partners, says in a news release.

Ara Partners specializes in investments in the decarbonization sector.

Founded in 1923, VAC was owned by technology conglomerate Siemens for more than 65 years. Ohio’s OM Group acquired VAC in 2011. Four years later, Apollo purchased OM Group for more than $1 billion, putting VAC in the hands of the asset manager.

As of June 30, Ara Partners had about $4.4 billion in assets under management, while Apollo had $617 billion in assets under management.