ELECTRON-ELECTRON INTERACTIONS AND SUPERCONDUCTING FLUCTUATIONS IN WEAKLY LOCALIZED K3C60

Magnetotransport studies on superconducting K3C60 films are presented. These films are a three-dimensional (3D) weakly localized system with strong electron-electron interactions, reflected by the large positiv e magnetoresistance (MR). The effects of superconducting fluctuations on the MR are observed in this 3D weakly localized system. The localiz ation is primarily caused by doping-induced disorder rather than granu larity, and the upper critical field H(c)2(T) follows the Werthamer-He lfand-Hohenberg model. An electron mean free path of 10-20 angstrom is estimated in the normal state just above T(c).