Evidence of fully gapped superconductivity in NbReSi: A combined <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>μ</mml:mi><mml:mi>SR</mml:mi></mml:math> and NMR study

We report a comprehensive study of the noncentrosymmetric NbReSi superconductor by means muon-spin rotation and relaxation ($\mu$SR) nuclear magnetic resonance (NMR) techniques. is bulk with $T_c = 6.5$ K, characterized large upper critical field, which exceeds Pauli limit. Both superfluid density $\rho_\mathrm{sc}(T)$ (determined via transverse-field $\mu$SR) spin-lattice rate $T_1^{-1}(T)$ NMR) suggest nodeless superconductivity (SC) in NbReSi. also find signatures multigap SC, here evidenced field-dependent electronic specific-heat coefficient. The absence spontaneous fields below $T_c$, as evinced from zero-field $\mu$SR measurements, indicates preserved time-reversal symmetry superconducting state Finally, we discuss possible reasons for unusually field NbReSi, most likely arising its anisotropic crystal structure.