= Co, Ni, Ir, Pt)

The discovery of unconventional superconductivity in a heavy-fermion antiferromagnet CePt₃Si has ignited remarkable interest in studying non-centrosymmetric (NCS) superconductors. The lack of an inversion center in this crystal structure induces an intrinsic electric field gradient that gives rise to antisymmetric spin-orbit coupling. As a result the spin degeneracy of electronic bands is lifted, which may develop parity-mixed superconducting state. We present our study on the weakly correlated Th-based alloys ThTSi (T = Co, Ni, Ir, Pt), crystallizing with a NCS structure like LaPtSi (a superconductor at T_C = 3.35 K). We discuss the variation of superconducting transitions with transition metals based on our experimental results as well as band calculations.