We report a study of the noncentrosymmetric TaReSi superconductor by means of
muon-spin rotation and relaxation (μSR) technique, complemented by
electronic band-structure calculations. Its superconductivity, with Tc​ = 5.5
K and upper critical field μ0​Hc2​(0)∼ 3.4 T, was
characterized via electrical-resistivity- and magnetic-susceptibility
measurements. The temperature-dependent superfluid density, obtained from
transverse-field μSR, suggests a fully-gapped superconducting state in
TaReSi, with an energy gap Δ0​ = 0.79 meV and a magnetic penetration
depth λ0​ = 562 nm. The absence of a spontaneous magnetization below
Tc​, as confirmed by zero-field μSR, 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 non\-triv\-i\-al electronic bands with intrinsic
superconductivity, TaReSi is a promising material for investigating the
topological aspects of noncentrosymmetric superconductors.Comment: 9 pages, 9 figures; accepted by Phys. Rev.