Electrical transport properties of A4C60 (A=Li, Na, and Rb) under pressure

In search of structural phase transformations, the electrical resistances of the alkali metal-intercalated fullerene compounds Li4C60, Na4C60, and Rb4C60 have been measured as functions of temperature and pressure. The compounds have different lattice structures, and in the first two, the fullerene molecules form two-dimensional covalently bonded polymer lattices. No phase changes could be identified over the ranges 100-400K and 0-2GPa. All materials are semiconducting under the conditions studied, and we see no strong dependence of the band gaps on pressure.