Superconductivity in the polymeric phase of Na2CsC60

We have studied the reversible pressure induced structural transition (primitive cubic to polymeric monoclinic) of Na2CsCGoand the superconductivity in both phases. We have established that the polymeric phase of Na2CsC60 is superconducting with an ambient pressure transition temperature about 3 K lower than that for the primitive cubic phase. We believe that an analogous lowering of the transition temperature in the corresponding phase of NazRbCGOeither leads to a very low transition temperature or to a total absence of superconductivity.