  We investigate direct detection signatures of dark matter particles
interacting with quarks via a light spin-0 mediator with general CP phases.
Since tree-level scattering may be strongly suppressed in the non-relativistic
limit, loop contributions play an important role and can lead to observable
signals in near-future experiments. We study the phenomenology of different
mediator masses and CP phases with an emphasis on scenarios with maximal CP
violation and Higgs portal models. Intriguingly, the sum of the rates obtained
at tree- and loop-level can give a characteristic recoil spectrum not
obtainable from a single type of interaction. We furthermore develop a novel
method for decomposing the two-loop contribution to effective interactions
between dark matter and gluons into two separate one-loop diagrams, which in
our case substantially simplifies the calculation of the important top-quark
contribution.
