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Superconductivity in intercalated group-IV honeycomb structures

We present a theoretical investigation on electron-phonon superconductivity of honeycomb MX$_2$ layered structures. Where X is one element of the group-IV (C, Si or Ge) and M an alkali or an alkaline-earth metal. Among the studied composition we predict a $T_c$ of 7 K in RbGe$_2$, 9 K in RbSi$_2$ and 11 K in SrC$_2$. All these compounds feature a strongly anisotropic superconducting gap. Our results show that despite the different doping and structural properties, the three families of materials fall into a similar description of its superconducting behavior. This allows us to estimate an upper critical temperature of about 20 K for the class of intercalated group-IV structures, including intercalated graphite and doped graphene.