Thermodynamic and electrical transport properties of UTe(2 )under uniaxial stress

Despite intense experimental efforts, the nature of the unconventional superconducting order parameter of UTe2 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 UTe2 under compressive uniaxial stress sigma applied along different crystallographic directions. We find that the critical temperature T-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-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) asymptotic to 0.17 GPa. This result suggests that the superconducting order parameter of UTe2 may be single component at ambient pressure.