Fullerides of alkaline-earth metals

Synchrotron radiation photoemission studies show that the mixing of Mg, Sr, and Ba with ${\mathrm{C}}_{60}$ yields metallic (Sr and Ba) and nonmetallic (Mg) fullerides. In all cases, fulleride formation leads to the occupation of hybrid bands near the Fermi level that are derived from ${\mathrm{C}}_{60}$ states and the s states of the alkaline-earth atoms. The nonmetallic character of ${\mathrm{Mg}}_{\mathit{x}}$ ${\mathrm{C}}_{60}$ probably reflects electron correlation effects, and metallic ${\mathrm{Sr}}_{\mathit{x}}$ ${\mathrm{C}}_{60}$ and ${\mathrm{Ba}}_{\mathit{x}}$ ${\mathrm{C}}_{60}$ fullerides are candidates for superconductivity.