The temperature dependence of the surface resistance of Rb3C60 at 9.2
GHz has been measured from 370 to 5 K. As well as the expected drop at
the superconducting transition temperature, anomalous changes are obs
erved at 370 and 190 K and attributed to phase transitions in the mate
rial. The dc and ac magnetic field dependence of the surface resistanc
e in the superconducting state is measured. Both low dc and ac magneti
c field weak link induced absorption are observed as well as high dc m
agnetic field vortex induced dissipation.