  The explanation of the large CP asymmetries in $D^0\to (\pi^+\pi^-, K^+K^-)$
decays observed by the LHCb collaboration is likely to call for new physics
beyond the CKM paradigm. We explore new contributions caused by the
color-sextet scalar diquark, and demonstrate that the diquark with the mass of
order 1 TeV and nominal couplings with quarks can generate the CP asymmetries
at the percent level. Using the experimental data on branching ratios and CP
asymmetries of $D^0\to (\pi^+\pi^-, K^+K^-)$, we derive the constraints on the
diquark mass and couplings, which can be further examined on hadron colliders
in the dijet final states.
