  The search for superconductivity in materials iso-structural and
iso-electronic with magnesium diboride, MgB2, has not yielded results with Tc
near 39K. In particular, Lithium borocarbide, LiBC, and its modification
Li0.5BC, proved to be non-superconducting. Using our materials-specific
condition for superconductivity and the symmetry principles for superconductor
search, we show that LiBC cannot be a superconductor. By replacing C in LiBC
with Si we achieve valence electron count (Ne) and atomic number (Z) symmetry
with MgB2. We therefore predict that Lithium boron silicon, LiBSi, should be a
superconductor with Tc comparable to MgB2.
