Fermi-liquid behavior in the electrical resistivity of K3C60 and Rb3C60

We report on the electrical resistivity of K3C60 and Rb3C60 thin films. These films, grown at elevated temperatures, are highly textured and consist of large single-crystal grains. The films exhibit metallic behavior up to 500 K, with residual resistivities of 1.2 mΩ cm. The low-temperature (T) resistivity exhibits a T2 dependence. We suggest that it is dominated by electron-electron interactions, and we find quantitative agreement not only with estimates based on the electron density and the bandwidth, but also with other narrow band systems. The electron-phonon interactions only become important for the resistivity above room temperature, because these phonons correspond to high-frequency vibrations of the C60 molecule. Nevertheless, virtual excitations of these same high-energy phonons are responsible for the superconductivity. Using similar criteria of conventional organic superconductors, we find that these materials are dominated at all temperatures by electron-phonon interactions