  We consider a model in which baryogenesis occurs at low scale, at a
temperature below the electroweak phase transition. This model involves new
diquark-type scalars which carry baryon number. Baryon number violation is
introduced in the scalar potential, permitting $\Delta B=2$ violating process
involving Standard Model quarks while avoiding stringent proton decay
constraints. Depending on their quantum number assignment, the diquark-type
scalars can couple to either right or left handed quarks, or to both. We show
that this model can provide a viable explanation of the baryon asymmetry of the
universe provided that the coupling to left handed quarks are present. However,
the coexistence of couplings to left and right handed quarks introduces
important phenomenological constraints on the model, such as radiative
contributions to quark masses and the generation of electric dipole moments for
nuclei, which probe the CP even and CP odd products of the relevant couplings
constants, respectively. We demonstrate that the strongest such constraints
arise from electric dipole moment measurements of the neutron and $^{199}$Hg.
These constraints are sufficiently strong that, in the absence of an intricate
flavor structure, baryogenesis must be dominated by the couplings of the new
scalars to left handed quarks.
