We study the specific heat of single-crystal ${\mathrm{UPt}}_3$ for uniaxial stress 0≤S≤4 kbar. For S∥c^, the lower and upper superconducting transitions move towards each other in temperature and merge by S=2 kbar and T=485 mK. In the normal state, the Sommerfeld constant γ increases 12% by 2 kbar and then plateaus. By contrast, for S∥a^, γ decreases steadily and the onset ${\mathit{T}}_{\mathit{c}}$’s of the two superconducting transitions remain essentially unchanged, although the specific-heat peaks broaden markedly. Residual strain in the basal plane may account for some crystals of ${\mathrm{UPt}}_3$ showing only one broad superconducting transition.

• Received 30 September 1991

DOI:https://doi.org/10.1103/PhysRevLett.68.1597