SUPERCONDUCTIVITY OF C60 COMPOUNDS

A series of C60 compounds is prepared using several K-Tl, Rb-Tl and Cs-Bi alloys in order to determine their superconducting properties. Samples with the nominal composition (RbTl1.5)3C60 show a superconducting onset temperature of 27.5 K. The temperature dependence of the magnetic penetration depth agrees with theoretical expressions derived for weak-coupled BCS-type superconductors in the clean local limit. The B(C2) (T) curves show a positive curvature near T(C). Susceptibility, X-ray and C-13 NMR measurements indicate a decomposition of the binary alloy during the preparation procedure and the presence of metallic T1 in the sample.