The large zero-sound attenuation just below the transition temperature $T_c$ to a superfluid state in liquid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ is anticipated above the transition by an excess attenuation over that for a normal Fermi liquid. The excess is greatest at $T_c$ but can be readily discerned at temperatures several percent above $T_c$. The excess is largest near melting pressure and exists adjacent to both ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-$A$ and ${}_{}{}^3{}_{}{}^{}\mathrm{He}$-$B$.

• Received 5 May 1978

DOI:https://doi.org/10.1103/PhysRevLett.41.561