US Senator Tommy Tuberville (R-AL) and five members of Congress sent a letter on Monday to Merrick Garland, Attorney General of the United States, and Gary Gensler, head of the Securities and Exchange Commission (SEC), about the conduct of Prometheum. The latter is an SEC- registered digital asset company that may have accepted money and technology from a China-based firm, and hid the fact from US lawmakers, they allege.