  We show that an in-plane Zeeman field applied to non-centrosymmetric Ising
superconductors converts singlet $s$-wave Cooper pairs to equal-spin triplet
$if$ pairs, leading to an enhancement of the critical transition line beyond
expected from Ising spin-orbit coupling. Singlet to triplet conversion relates
to a phase transformation due to spin rotation by the Zeeman field and has a
geometric origin. The discussion is especially relevant, but not limited to
monolayer transition metal dichalcogenides.
