Anisotropic Migdal-Eliashberg analysis of superconductivity in layered Li-Mg-B compounds*

LiB, a predicted compound analogous to the MgB₂ superconductor, has been recently synthesized via cold compression and quenched to ambient pressure. We reinvestigate the superconducting properties of LiB and find that the electron-phonon coupling anisotropy is as essential as in MgB₂. Using the anisotropic Eliashberg formalism, we predict a critical temperature (T_c) to be in the 32-42 K range, three times higher than prior estimates based on isotropic calculations. We probe other Li-Mg-B binary and ternary layered materials and find metastable phases with T_c close to or even 10-20% above the record 39 K value in MgB₂.