MP Materials surged Wednesday on a deal with the U.S. Department of Defense and the Saudi Arabian Mining Company, Maaden, to develop a rare earth refinery in the kingdom. The U.S. rare earth miner's stock was last up about 9%. MP and the Pentagon will hold a 49% stake in the joint venture, the company said. Maaden's position will be no less than 51%. The Defense Department will finance the U.S. portion of the venture with MP providing technical and marketing expertise. The binding agreement to form the join ...