SUPERCONDUCTIVITY AT 40K IN CESIUM DOPED C-60

We report superconductivity in Cs-3 C-60 at 40K using ac susceptibilit y measurements under hydrostatic conditions up to 15 kbar. Cs-3 C-60 w as prepared by reaction of C-60 with Cs in liquid ammonia, followed by heating at 150 degrees C. This route circumvents formation of the ene rgetically more stable CS1 C-60 and Cs-4 C-60 phases. We have studied the synthesis and phase formation by measuring the symmetric A(g) pent agonal pinch mode of C-60 using Raman spectroscopy. Whereas Raman spec troscopy indicates homogeneous charge transfer of three electrons, x-r ay diffraction indicates two phases other than the commonly observed f ee structure. This superconducting transition temperature is considera bly higher than for known doped C-60 compounds and intermetallic compo unds.