The superconductor-insulator transition in a transverse magnetic field is studied in a highly disordered MoC film with the product of the Fermi momentum and the mean free path kF*l close to unity. Surprisingly, the Zeeman paramagnetic effects dominate over orbital coupling on both sides of the transition [1]. In the superconducting state it is evidenced by a high upper critical magnetic field Bc2, by its square-root dependence on temperature, as well as by the Zeeman splitting of the quasiparticle density of states measured by scanning tunneling microscopy. At Bc2 a logarithmic anomaly in DOS is observed. This anomaly is further enhanced in an increasing magnetic field, which is explained by the Zeeman splitting of the Altshuler-Aronov DOS driving the system into a more insulating or resistive state. A spin-dependent Altshuler-Aronov correction is also needed to explain the transport behavior above Bc2.

[1] M. Žemlička et al., Phys. Rev. B 102 (2020), 180508(R).