Nonsaturating linear resistivity up to 900 K in MgB2

In this work, we report resistivity measurements on MgB2 polycrystalline samples with increasing degree of doping (disorder) up to temperatures higher than 900 K. In all cases the normal state curves are linear with increasing temperatures, with no sign of flattening or downward bending (saturation) at high temperature. This behavior, in sharp contrast to what is observed in superconducting compounds such as A15 and Chevrel phases, can be explained considering the dominant pi contribution to the electric conduction, together with the smaller electron-phonon coupling of pi carriers in MgB2, as compared to characteristic coupling strength of those compounds. This indicates that in MgB2 the disorder introduced in the lattice by thermal oscillations even at 900 K can still be considered as a perturbation within the Boltzmann description of transport.