FAA Order 8130.2M — Operating Limitation 13
Appendix D · Table D-1 · p. p171
This aircraft must be operated with a second in command (SIC). The SIC must comply with the SIC qualification and familiarization requirements specified in § 61.55. The SIC may hold a pilot certificate with airplane multiengine land, rotorcraft helicopter, or powered-lift, provided no passengers, as defined in § 61.1, are carried on board. The SIC must hold a pilot certificate with powered-lift category if any other persons are on board.
Verify it yourself: the eyeball above opens the exact page of Order 8130.2M with this limitation highlighted.