Divalent scandium atoms in the cage of C84.

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}$${\mathrm{O}}_{3}$). This suggests that Sc atoms encapsulated in ${\mathrm{C}}_{84}$ take an intermediate valency between those of the metal (${\mathrm{Sc}}^{0\ifmmode\pm\else\textpm\fi{}}$) and the oxide (${\mathrm{Sc}}^{3+}$). UPS shows that solid ${\mathrm{Sc}}_{2}$${\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.