ELECTRICAL TRANSPORT-PROPERTIES OF THE POTASSIUM DOPED BULK FULLERENE, KXC60

Temperature dependent thermoelectric power(TEP) and conductivity of the potassium doped bulk fullerene, KxC60, of different potassium doping concentrations are reported. The potassium contents are determined by chemical analyses. The resistivity drop at T = 18K has been confirmed. Although, the room temperature resistivity values are more or less the same for various KxC60 samples (typically sigma-RT = 10 S/cm), the TEP values are very much different. The sign of TEP is positive and its temperature dependence shows a big transition at around T = 150K. Interesting observation is that the TEP drops to zero at around 60K approximately 80K for certain samples whose resistivity keep increasing at this temperature region.