Superconductivity in LixCsC60 fullerides

Superconductivity lost in Li2CsC60 is recovered when the t(1u) band is furt her filled through introduction of additional Li. Superconducting transitio n temperatures, T-c of 10.5 K and 8 K are observed for Li3CsC60 and Li4CsC6 0, respectively. The band filling of nonsuperconducting Li2CsC60 is establi shed by Raman spectroscopy to be n=2.5, while that for superconducting Li3C sC60 is around n=3. These results indicate that appearance of superconducti vity in alkali fullerides with stoichiometry A(3)C(60) is sensitively contr olled by the filling of the r(1u) band and that n = 3 plays an especially i mportant role. [S0163-1829(99)51210-1].