Divalent scandium atoms in the cage ofC84

X-ray spectroscopy (XPS) and ultraviolet photoemission spectroscopy (UPS) have been performed on an endohedral fullerene ${\mathrm{Sc}}_2$ ${\mathrm{C}}_{84}$. The Sc 2p XPS core level of ${\mathrm{Sc}}_2$ ${\mathrm{C}}_{84}$ was found to be located just between those of the metal and the oxide (${\mathrm{Sc}}_2$ ${\mathrm{O}}_3$). This suggests that Sc atoms encapsulated in ${\mathrm{C}}_{84}$ take an intermediate valency between those of the metal (${\mathrm{Sc}}^{0\pm }$) and the oxide (${\mathrm{Sc}}^{3+}$). UPS shows that solid ${\mathrm{Sc}}_2$ ${\mathrm{C}}_{84}$ is an insulator with an energy gap of about 1 eV. It was also found that ${\mathrm{Sc}}_2$ ${\mathrm{C}}_{84}$ does not undergo thermal decomposition upon evaporation and is extremely stable even in the air.