Increased transition temperature in superconducting Na2CsC60 by intercalation of ammonia

The alkali-metal fulleride Na2CsC60 is a f.c.c. superconductor with and a value of 14.132 angstroms and a transition temperature (Tc) of 10.5 K. Since cations can occupy the octahedral site of the fulleride, attempts were made to introduce molecular ammonia (NH3) to Na2CsC60. Ammonia was introduced by exposing the sample to 380 torr of NH3 gas distilled from a sodium/liquid-ammonia solution through a vacuum manifold. Introduction of the ion resulted in an increase in a to 14.473 angstroms and an increase in Tc to 29.6K.