COPPER AND INDIUM KNIGHT-SHIFTS ABOVE AND BELOW FIRST-ORDER VALENCE TRANSITION IN YBINCU4

Cu-63 and In-115 Knight shifts were measured for YbInCu4 both above an d below the first-order valence transition temperature T-upsilon. The hyperfine coupling constants of Cu-63, which are small, of the order o f the classical lattice dipole field, increase markedly below T-upsilo n, white that of In-115 exhibits an only slight change at T-upsilon, s uggesting different roles of the ligands in the valence transition.