  Since the current evidence of its existence is revealed only through its
gravitational influence, the way dark matter couples to gravity must be then of
primary importance. Here, unlike the standard model sector which is typically
coupled to metric, dark matter is supposed to couple only to spacetime affine
connection through a $Z_2$-symmetry breaking term. We show that this structure
leads to a coupling between dark matter, which is considered scalar, and the
standard model Higgs potential. This induces dark matter decays into standard
model particles through the Higgs which acts as a portal between the visible
and the dark sectors. We study thoroughly the resulting decay modes for various
mass ranges, and provide relevant bounds on the nonminimal coupling to affine
gravity in line with observational data. Moreover, we find that the coupling to
Higgs can be sufficiently large to facilitate production of dark matter lighter
than 10 GeV at current and future high energy colliders.
