New Three-Dimensionalk→·p→Model for the Electronic Structure ofA−15Compounds

We introduce a three-dimensional $\overrightarrow{\mathrm{k}}·\overrightarrow{\mathrm{p}}$ model for the electronic structure of $A-15\mathrm{}$ compounds based upon a six-dimensional irreducible representation $R\left(4\right)\mathrm{}$ of the space group ${O_h}^3-Pn3m$. By locating the Fermi level near the maximum in the density of states, the temperature-dependent free energy accounts quantitatively for anomalous normal-state physical properties of ${\mathrm{Nb}}_3$Sn and other $A-15\mathrm{}$ compounds. No use is made of tight-binding approximations nor assumptions of one dimensionality or quasi one dimensionality.