Ultraviolet photoelectron spectra of Lu atoms encapsulated C2v-C82 fullerenes

► UPS onsets of Lu atom(s) encapsulated fullerenes indicate their semi-conductive nature. ► Lu4f7/2 and Lu4f5/2 levels of the encapsulated metal are observed for the first finding in UPS. ► The electronic configuration of Lu2@C82 might be (Lu3+)2@C826−. ► Possibly Lu atoms in Lu2C2@C82 are Lu−3+δ for resulting hybridization or back donation.