Magnetic-field, pressure, and temperature scaling of the first-order valence transition in pure and doped YbInCu4

We report measurements of the high-field (H less than or equal to 30 T) magnetoresistance R(H,T) of pure and doped YbInCu4. A hysteretic transition is observed which we take to be the field-induced variant of the first-order valence transition observed;at 42 K in YbInCu4 for H=0 T. Applied pressure suppresses the:valence transition to lower temperature. By properly scaling the (H-v,T-v) data extracted from the resistance measurements, we can collapse all of the pressure-dependent data, as well as that from doped variants of YbInCu4 at ambient pressure, onto a universal H-T phase diagram. This suggests that a single energy scale is associated with the valence transition.