RESISTIVITY SATURATION IN ALKALI-DOPED C-60

The high-temperature resisitivity of K and Rb-doped C-60 single crysta ls was measured with pulsed heating techniques and analyzed within the parallel-resistor extension to Bloch-Boltzmann transport theory. Rb3C 60 exhibits resitivity saturation with p(sat)(Rb) approximate to 6 +/- 3m Omega-cm, corresponding to a saturation mean free path of l(sat)(R b) approximate to 1 +/- 0.5 Angstrom. In contrast K3C60 does not show signs of resistivity saturation up to 800 K, suggesting that p(sat)(K) > 3m Omega-cm and l(sat)(K) < 1.5 Angstrom. The electronic stakes at high temperature have a characteristic length scale significantly smal ler than the fcc lattice constant.