ELECTRONIC TRANSPORT-PROPERTIES OF KXC70 THIN-FILMS .2.

The transport properties of KxC70 thin films doped to their maximum co nductivity are reported. At this doping level, KxC70 (nominally K4C70) , with room-temperature-conductivity (sigma) values ranging between ap proximately 10-600 S/cm, is characteristic of a disordered metal near the Anderson-localization regime, whose sigma values are larger than t he minimum metallic conductivity. The conduction-band width is estimat ed as 0.2-0.6 eV and the charge transport is modeled by the fluctuatio n-induced-tunneling model. The temperature dependence of the thermopow er (S) and Hall coefficient (R(H)) are similar to that for superconduc ting K3C60 and graphite intercalation compounds. Thermopower anomalies in S(T) are observed in the same temperature range 80 < T < 100 K as the sign change of R(H)(T), reflecting a possible change in structure or scattering process in this T range. The temperature and magnetic-fi eld dependence of the magnetoresistance of KxC70, also similar to that of K3C60, is compared with weak-localization theory, electron-electro n interaction theory, and a two-band-metal model. Based on these model s, we extract information about the intrinsic conductivity of the meta llic regions. No superconducting transition in KxC70 is observed above 1.35 K.