We report a study of the noncentrosymmetric TaReSi superconductor by means of the muon-spin rotation and relaxation $\left(\mu \mathrm{SR}\right)$ technique, complemented by electronic band-structure calculations. Its superconductivity, with $T_c=5.5\text{K}$ and upper critical field ${\mu }_0{H}_{\mathrm{c}2}\left(0\right)\sim 3.4\text{T}$, was characterized via electrical-resistivity and magnetic-susceptibility measurements. The temperature-dependent superfluid density, obtained from transverse-field $\mu \mathrm{SR}$, suggests a fully gapped superconducting state in TaReSi, with an energy gap ${\mathrm{\Delta }}_0=0.79\text{meV}$ and a magnetic penetration depth ${\lambda }_0=562\text{nm}$. The absence of a spontaneous magnetization below $T_c$, as confirmed by zero-field $\mu \mathrm{SR}$, indicates a preserved time-reversal symmetry in the superconducting state. The density of states near the Fermi level is dominated by the Ta- and Re-$5d$ orbitals, which account for the relatively large band splitting due to the antisymmetric spin-orbit coupling. In its normal state, TaReSi behaves as a three-dimensional Kramers nodal-line semimetal, characterized by an hourglass-shaped dispersion protected by glide reflection. By combining nontrivial electronic bands with intrinsic superconductivity, TaReSi is a promising material for investigating the topological aspects of noncentrosymmetric superconductors.

• Received 8 September 2022
• Revised 19 May 2023
• Accepted 26 May 2023

DOI:https://doi.org/10.1103/PhysRevB.107.224504