The company may be under criminal investigation for alleged irregularities in its Medicare business—but it's been touched by the Warren Buffett effect.

Shares of health insurance company UnitedHealth (NYSE:UNH) jumped 3.3% in the afternoon session after its board of directors authorized the payment of a quarterly cash dividend, signaling a commitment to shareholder returns.

This investment signifies Buffett's re-entry into UNH after liquidating his entire position back in 2010, indicating that he perceives significant value at