Ultrasonic attenuation and velocity measurements in the normal state of the heavy fermion superconductor UPt3

UPt₃ is a superconducting heavy fermion compound showing unconventional properties in the superconducting state. Longitudinal sound attenuation and velocity measurements in the normal state of UPt₃ from 2 K to 300 K are presented for frequencies ranging from 85 MHz to 850 MHz, in a magnetic field up to 8 T. Attention is focused on the attenuation absorption peak developing at temperatures below 40 K, which is accompanied by a rapid increase in velocity. The center of this peak is located at about 10.5 K and, within the experimental resolution, its position is frequency-independent. The amplitude of this peak is found to be proportional to the square of the sound frequency. With an increasing applied magnetic field, the center of the peak is found to move to lower temperatures while the amplitude of the peak increases