  We present a compositional and structural investigation of silicene,
germanene, and stanene bilayers from first-principles. Due to the staggering of
the individual layers, several stacking patterns are possible, most of which
are not available to the bilayer graphene. This structural variety, in
conjunction with the presence of the spin-orbit coupling, unveil a diversity of
the electronic properties, with the appearance of distinct band features,
including orbital hybridization and band inversion. We show that for particular
cases, the intrinsic spin Hall response exhibits signatures of non-trivial
electronic band topology, making these structures promising candidates to probe
Dirac-like physics.
