Max-Planck-Institut für Festkörperforschung, Stuttgart;
Complex Systems Theory Branch, Naval Research Laboratory, Washington, D.C. 20375-5000

We show that hopping via alkali atoms plays an important role for the t_1u band of A₄C₆₀ (A=K, Rb), in strong contrast to A₃C₆₀. Thus the t_1u band is broadened by more than 40% by the presence of the alkali atoms. The difference between A₄C₆₀ and A₃C₆₀ is in particular due to the less symmetric location of the alkali atoms in A₄C₆₀ we present tightbinding and ab initio bandstructure calculations to support our conclusions.

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Physical Review B, 57 2159-62, 1998.