T. Yildirim et al., SYNTHESIS AND PROPERTIES OF MIXED ALKALI-METAL-ALKALINE-EARTH FULLERIDES, Physical review. B, Condensed matter, 54(17), 1996, pp. 11981-11984
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.