Anisotropy of electronic transport in the iron-pnictide superconductor Ba(Fe,Co)$_2$As$_2$

The anisotropy of electrical resistivity in the iron pnictide superconductor Ba(Fe,Co)$_2$As$_2$ has been studied using the Montgomery technique and direct transport measurements in single crystals cut along principal directions of the conductivity tensor (tetragonal c-axis and a-direction perpendicular to it). A good quantitative agreement is found between two sets of data, with a $\rho_c/ \rho_a$ anisotropy of 5 $\pm$ 1 just above the superconducting transition temperature. This is in very good agreement with expectations based on the anisotropy of the critical fields, suggestive of orbital limiting of superconductivity at T$_c$.