  Systems with strong spin-orbit coupling have been a topic of fundamental
interest in condensed matter physics due to the exotic topological phases and
the unconventional phenomenon they exhibit. In this particular study, we have
investigated the superconductivity in the transition-metal ternary
noncentrosymmetric compounds LaMSi (M = Ni, Pt) with different spin-orbit
coupling strength, using muon-spin rotation and relaxation measurements.
Transverse-field measurements made in the vortex state indicate that the
superconductivity in both materials is fully gapped, with a conventional s-wave
pairing symmetry and BCS-like magnitudes for the zero-temperature gap energies.
Zero field measurements suggest a time-reversal symmetry preserved
superconductivity in both the systems, though a small increase in muon
depolarization is observed upon decreasing temperature. However, this has been
attributed to quasi-static magnetic fluctuations.
