SYNTHESIS AND PROPERTIES OF MIXED ALKALI-METAL-ALKALINE-EARTH FULLERIDES

A new class of fullerides, MBa(2)C(60) (M=K, Rb, or Cs) and MBaCsC(60) , allows us to study the effect of molecular valence on electronic str ucture while maintaining the crystal structure of M(3)C(60) supercondu ctors. X-ray diffraction and Raman scattering show that these are face -centered cubic with pentavalent and quadrivalent C-60's, respectively . We find no evidence for superconductivity down to 0.5 K, while elect ron spin resonance indicates weakly metallic behavior. C-13 NMR indica tes strong dynamical disorder above room temperature, which may be rel ated to the anisotropic crystal field induced by cations of different valence.