  We report the first measurement of charmed-hadron ($D^0$) production via the
hadronic decay channel ($D^0\rightarrow K^- + \pi^+$) in Au+Au collisions at
$\sqrt{s_{_{\mathrm{NN}}}}$ = 200\,GeV with the STAR experiment. The charm
production cross-section per nucleon-nucleon collision at mid-rapidity scales
with the number of binary collisions, $N_{bin}$, from $p$+$p$ to central Au+Au
collisions. The $D^0$ meson yields in central Au+Au collisions are strongly
suppressed compared to those in $p$+$p$ scaled by $N_{bin}$, for transverse
momenta $p_{T}>3$ GeV/$c$, demonstrating significant energy loss of charm
quarks in the hot and dense medium. An enhancement at intermediate $p_{T}$ is
also observed. Model calculations including strong charm-medium interactions
and coalescence hadronization describe our measurements.
