Large critical fields in superconducting Ti₄Ir₂O from anomalous pseudospin

The recently synthesized superconductor Ti₄Ir₂O was reported to exhibit a large upper critical field that strongly violates the Pauli paramagnetic limit. This is puzzling since this material is cubic and preserves inversion symmetry, so spin-orbit coupling is not expected to qualitatively change the usual superconducting paramagnetic response. Here, combining density functional theory calculations and analytic kp theories, we reveal that an anomalous spin-orbit driven Kramers degenerate pseudospin provides a natural explanation for the observations. Our results provide new insight into the role of spin-orbit coupling in non-symmorphic materials.