Stability and magnetism in FeC$_{\mathrm{2}}$ monolayer

We report a new FeC$_{\mathrm{2}}$ sheet containing C$_{\mathrm{2}}$ dimers, which can be chemically exfoliated from bulk ThFeC$_{\mathrm{2}}$ phase. Using density functional theory combined with AIMD and phonon dispersion calculation, we found that upon exfoliation from bulk ThFeC$_{\mathrm{2}}$, the FeC$_{\mathrm{2}}$ sheet changes its symmetry from \textit{Amm}2 to \textit{Pmmn}, while retaining its robust dynamical, thermal and mechanical stability. In sharp contrast to the metallic and paramagnetic bulk phase of ThFeC$_{\mathrm{2\thinspace }}$and the recently reported TiC$_{\mathrm{2}}$ sheet,$_{\mathrm{\thinspace }}$the$_{\mathrm{\thinspace }}$exfoliated FeC$_{\mathrm{2}}$ sheet$_{\mathrm{\thinspace }}$is half-metallic and ferromagnetic with a Curie-temperature of 245 K, making it a promising candidate for spintroinc applications.