Jensen Huang, the leader of Nvidia who is under investigation for an affair with a woman who U.S. intelligence determined is a Chinese spy, also had an extramarital relationship with an executive who reports to him, according to five people who worked at the company. The relationship, which has not been previously reported, was with Kimberly Powell, Nvidia’s vice president of health care, said the people, who spoke under the condition of anonymity to describe sensitive information. Under Nvidia’s code of conduct, employees are told to “avoid situations where our actions create conflict” including “personal relationships,” and the company states...