  Within first-principles calculations, we explore superconductivity in
Ca-intercalated bilayer silicene compound, Si2CaSi2. This arises from the
coupling of interlayer flower-like \Gamma-centered Fermi surface formed by the
hybridization of Ca-3d and Si-3pz orbitals with low-energy out-of-plane
vibrations enabled by silicene's buckling. The consequent large electron-phonon
coupling, as evident from the Eliashberg spectral function leads to
superconductivity below 5.4 K in this two-dimensional covalent system. Our
results reveal the key control parameters to achieve superconductivity in
experimentally synthesizable silicon-based thin materials that can find diverse
applications.
