  We investigate the weak decays of $\bar B_{s}^{0}$ and $\Lambda_{b}$ to charm
hadrons based on the dynamical supersymmetry between the $\bar s$ quark and the
$ud$ diquark. We derive a new sum rule relating the decay rates of the
processes $\bar B_{s}^{0} \to D_{s}^{+} P^{-}$, $\bar B_{s}^{0} \to D_{s}^{*+}
P^{-}$ and $\Lambda_{b} \to \Lambda_{c} P^{-}$, where $P^{-}$ is a negatively
charged meson, such as $\pi^{-}$ and $K^{-}$. It is found that the observed
decay rates satisfy the sum rule very well. This implies that the supersymmetry
between the $\bar s$ quark and the $ud$ diquark is also seen in the
wavefunctions of the heavy hadrons and suggests that the $ud$ diquark can be
regarded as a valid effective constituent for heavy hadrons.
