Yb and Yb-K fulleride formation, bonding, and electrical character

Yb mixing with ${\mathrm{C}}_{60}$ produces a phase with approximately two Yb atoms per fullerene but showed no indication of ${\mathrm{Yb}}_{\mathit{x}}$ ${\mathrm{C}}_{60}$ phases with x=3, 4, and 6. Thin-film resistivity measurements indicate that this Yb fulleride is a semiconductor with a resistivity of 100 mΩ cm at 300 K and 38 mΩ cm at 400 K. Yb condensation onto metallic ${\mathrm{K}}_3$ ${\mathrm{C}}_{60}$ produces a ternary compound.