The president-elect and his family have a direct and potentially lucrative stake in the sale of a cryptocurrency product that surged in value in the hours after going on sale, days before his inauguration.

Regulators filed a lawsuit in federal court stemming from Mr. Musk’s $44 billion purchase of the social media company now called X.

The price of a single Bitcoin rose to six figures for the first time, an extraordinary level for a 16-year-old cryptocurrency once dismissed as a sideshow.

© Haley Jiang