  Heavy baryon/meson ratios $\Lambda_c/D^0$ and $\Lambda_b/\bar{B}^0$ in
relativistic heavy ion collisions are studied in the quark coalescence model.
For heavy baryons, we include production from coalescence of heavy quarks with
free light quarks as well as with bounded light diquarks that might exist in
the strongly coupled quark-gluon plasma produced in these collisions. Including
the contribution from decays of heavy hadron resonances and also that due to
fragmentation of heavy quarks that are left in the system after coalescence,
the resulting $\Lambda_c/D^0$ and $\Lambda_b/\bar{B}^0$ ratios in midrapidity
($|y|\le 0.5$) from central Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV are
about a factor of five and ten, respectively, larger than those given by the
thermal model, and about a factor of ten and twelve, respectively, larger than
corresponding ratios in the PYTHIA model for $pp$ collisions. These ratios are
reduced by a factor of about 1.6 if there are no diquarks in the quark-gluon
plasma. The transverse momentum dependence of the heavy baryon/meson ratios is
found to be sensitive to the heavy quark mass, with the $\Lambda_b/\bar{B}^0$
ratio being much flatter than the $\Lambda_c/D^0$ ratio. The latter peaks at
the transverse momentum $p_T^{} \simeq 0.8$ GeV but the peak shifts to $p_T^{}
\simeq 2$ GeV in the absence of diquarks.
