We report the first measurements of the attenuation of ultrasound in the basal plane of superconducting U${\mathrm{Pt}}_3$. Transverse sound propagating along the $b$ axis shows a marked anisotropy in its temperature dependence when the polarization is rotated in and out of the basal plane. For polarization in the basal plane the attenuation varies linearly with temperature down to 35 mK and the slope scales as the square of the frequency. Our results appear to indicate the presence of an additional attenuation mechanism when compared with recent theories of anisotropic superconductors in the dirty limit.

• Received 18 December 1985

DOI:https://doi.org/10.1103/PhysRevLett.56.1078