K-39 NMR-STUDY OF PHASE-TRANSITIONS AND ELECTRONIC-PROPERTIES IN K3C60

K-39 NMR signals from the orthorombic and tetrahedral sites are detect ed at high T, in K3C60. However below 210K a new K-39 line appears. It s characteristics are nearly identical to those found for the extra Rb -87 line observed below 400K in Rb3C60, which suggests that the low T structural and electronic properties of the superconducting A(3)C(60) compounds are quite similar. The T variations of the K-39 NMR shifts h ave been studied from the high T cubic phase down to the superconducti ng state. They are surprisingly found to be dominated by the variation of the orbital contributions.