Quasiparticle interference in antiferromagnetic parent compounds of iron-based superconductors

Recently reported quasiparticle interference imaging in underdoped Ca(Fe1-xCox)(2)As-2 shows pronounced C-2 asymmetry, which is interpreted as an indication of an electronic nematic phase with a unidirectional electron band, dispersive predominantly along the b axis of this orthorhombic material. On the other hand, even more recent transport measurements on untwinned samples show near isotropy of the resistivity in the ab plane, with slightly larger conductivity along a (and not b). We show that, in fact, both sets of data are consistent with the calculated ab initio Fermi surfaces, which have a decisively broken C-4 and yet similar Fermi velocity in both directions. This reconciles completely the apparent contradiction between the conclusions of the scanning tunneling microscopy and the transport experiments.