  Recent experiments on the silicon terminated $3\times 2$ SiC(100) surface
indicated an unexpected metallic character upon hydrogen adsorption. This
effect was attributed to the bonding of hydrogen to a row of Si atoms and to
the stabilization of a neighboring dangling bond row. Here, on the basis of
Density-Functional calculations, we show that multiple-layer adsorption of H at
the reconstructed surface is compatible with a different geometry: besides
saturating the topmost Si dangling bonds, H atoms are adsorbed at rather
unusual sites, \textit{i.e.} stable bridge positions above third-layer Si
dimers. The results thus suggest an alternative interpretation for the
electronic structure of the metallic surface
