Partial vapor pressures of potassium and C-60 were measured in all regions
of K-C-60 phase diagram by Knudsen cell mass spectrometry method; the Gibbs
energies of formation of KxC60 (x = 1,3,4,6) compounds were calculated. Ba
sed on our and literature data the phase diagram was built for K-C-60 syste
m at T=925 K.