  We propose a new mechanism which can introduce large $CP$ asymmetries in the
phase spaces of three-body decays of heavy baryons. In this mechanism, a large
$CP$ asymmetry is induced by the interference of two intermediate resonances,
which subsequently decay into two different combinations of final particles. We
apply this mechanism to the decay channel $\Lambda_b^0 \to p \pi^0\pi^-$, and
find that the differential $CP$ asymmetry can reach as large as $50\%$, while
the regional $CP$ asymmetry can reach as large as $16\%$ in the interference
region of the phase space.
