Despite intense experimental efforts, the nature of the unconventional superconducting order parameter of ${\mathrm{UTe}}_2$ remains elusive. This puzzle stems from reports of either a single or a double superconducting transition at ambient pressure as well as a complex pressure-temperature phase diagram. To address this issue, we measured the heat capacity and electrical resistivity of ${\mathrm{UTe}}_2$ under compressive uniaxial stress $\sigma$ applied along different crystallographic directions. We find that the critical temperature $T_{\mathrm{c}}$ of the single observed bulk superconducting transition decreases with $\sigma$ along [100] and [110] but increases with $\sigma$ along [001]. Aside from its effect on $T_{\mathrm{c}}$, $c$-axis stress leads to a significant piezoresistivity. Importantly, an in-plane shear stress ${\sigma }_{xy}$ does not induce any observable splitting of the superconducting transition over a stress range of ${\sigma }_{xy}\approx 0.17\mathrm{GPa}$. This result suggests that the superconducting order parameter of ${\mathrm{UTe}}_2$ may be single component at ambient pressure.

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• Heavy-fermion systems
• Superconductors
• Topological superconductors
• Unconventional superconductors
• Calorimetry
• Pressure effects
• Resistivity measurements
• Specific heat measurements