  By means of density functional theory the electronic structure of the MgB2
superconductor was characterised and compared with that of the related
iso-structural systems: AlB2, ZrB2, NbB2, and TaB2. Using the full-potential
linearized augmented plane waves (FP-LAPW) method and the generalised gradient
approximation, the electronic density distribution, density of states, and band
structures were obtained for these compounds. The electrical conductivity,
which cannot be easily measured in the c-direction, was calculated, in the
relaxation time approximation using band structure results. It was found that
the two-dimensional (2D) crystal structure character of these metallic
diborides is also reflected in the electronic charge distribution. This 2D
pattern is not completely seen in the electrical conductivity as it is, for
instance, in the superconductor high Tc cuprates. Indeed, it was found that, by
the electrical conductivity calculations, all these compounds have a bulk, yet
anisotropic, conductivity.
