Ultrasonic velocity determination of the phase diagram of UPt3

Abstract We report ultrasonic velocity measurements on two UPt 3 samples with three different field orientations (H⊥c, H//c and H∧c=45°). Velocity changes are observed at constant temperatures, as the field is swept, at the upper critical field H c2 and at the flux lattice transition H fl . Velocity changes are also observed at T c + the upper transition temperature and T c - the lower transition temperature as the temperature is swept at constant fields. Complete phase diagrams for UPt 3 obtained by a single measurement technique on the same samples in the H-T plane are presented.