  Dark matter interacting with the Standard Model fermions through new scalars
or pseudoscalars with flavour-diagonal couplings proportional to fermion mass
are well motivated theoretically, and provide a useful phenomenological model
with which to interpret experimental results. Two modes of dark matter
production from these models have been considered in the existing literature:
pairs of dark matter produced through top quark loops with an associated
monojet in the event, and pair production of dark matter with pairs of heavy
flavoured quarks (tops or bottoms). In this paper, we demonstrate that a third,
previously overlooked channel yields a non-negligible contribution to LHC dark
matter searches in these models. In spite of a generally lower production cross
section at LHC when compared to the associated top-pair channel, non-flavour
violating single top quark processes are kinematically favored and can
significantly increase the sensitivity to these models. Including dark matter
production in association with a single top quark through scalar or
pseudoscalar mediators, the exclusion limit set by the LHC searches for dark
matter can be improved by $30$--$90\%$, depending on the mass assumed for the
mediator particle.
