Abstract In the light of the tremendous progress that has been made in raising the transition temperature of the copper oxide superconductors. At present, the highest reported values of Tc for non-copper-oxide bulk superconductivity are 33 K in CsxRbyC60, and 30 K in Ba1-xKxBiO3. The recent discovery of superconductivity at 39 K in the sample binary ceramic compound magnesium diboride, MgB2(ref. 1), was therefore surprising. Indeed, this material has been known and structurally characterized since the mid 1950s, and is readily available from chemical suppliers. Here we try to addition of electrons to MgB2, through partial substitution of Al for Mg and a structural transition in Mg1-xAlxB2