Temperature dependence of ultrasonic attenuation in the superconducting state of the heavy fermion compound UPt3

Longitudinal ultrasonic attenuation at frequencies up to 450 MHz on a single crystal UPt₃ sample was measured in the superconducting state down to about 50 mK. A new technique was used, in which the resolution of both attenuation and velocity was significantly improved. After being normalized by the normal state attenuation, the superconducting attenuation at different frequencies exhibits identical power-law temperature dependence in the superconducting state of UPt₃. Discussions of these experimental results in comparison with theoretical models based on different types of order parameter are given