  Superconductors that possess both broken spatial inversion symmetry and
spin-orbit interactions exhibit a mix of spin singlet and triplet pairing.
Here, we report on measurements of the superconducting properties of
electron-doped, strained SrTiO3 films. These films have an enhanced
superconducting transition temperature and were previously shown to undergo a
transition to a polar phase prior to becoming superconducting. We show that
some films show signatures of an unusual superconducting state, such as an
in-plane critical field that is higher than both the paramagnetic and orbital
pair breaking limits. Moreover, nonreciprocal transport, which reflects the
ratio of odd versus even pairing interactions, is observed. Together, these
characteristics indicate that these films provide a tunable platform for
investigations of unconventional superconductivity.
