Energy bands and Fermi surface of ${\mathrm{Sr}}_2{\mathrm{RuO}}_4$

A method combining the extended Hückel theory and the tight-binding approximation is proposed to study the electronic properties of the layered noncuprate superconductor ${\mathrm{Sr}}_2{\mathrm{RuO}}_4.$ The band structure close to the Fermi level is obtained by integrating out all low-lying oxygen degrees of freedom allowing the determination of the energy spectra, the Fermi surface, and the total density of states. The results reproduces the main features of local-density approximation calculations near the Fermi energy. As an application of the approach here proposed, we have calculated the temperature dependence of the in-plane Hall coefficient considering the effect of the curvature of the Fermi surface.