  Infrared transmission, electron spin resonance, and X-ray diffraction
measurements show unambiguously that RbC$_{60}$ and KC$_{60}$ are stable in
air, in contrast to Rb$_{6}$C$_{60}$ which decomposes rapidly upon exposure.
The specimens studied transform into pure C$_{60}$ and other byproducts when
heated above $100\dd $C, approximately the temperature of the orthorhombic-fcc
phase transition. The stability of these compounds raises the possibility of
applying them as protective layers for the superconducting fullerides.
