Thermoelectric Power of Alkali DopedC60

Thermoelectric power of M 3 C 60 (M=K, Rb) exhibits nearly T -linear dependence with negative sign above the superconducting transition temperature. Small but clear deviation from the linear relation at low temperatures is ascribed to the phonon drag effect. Observed broad dip over ∼ 100 K and its small magnitude suggest that the anomaly is not related to the electron-intramolecular phonon interaction but to the electron-intermolecular phonon interaction. The electron-phonon coupling constant D and the phonon velocity are estimated to be ∼ 10 -1 eV and several km/sec, respectively. The small value for D is expected from the low Fermi energy obtained from the band calculation and the diffusion thermoelectric power.