Ultra-complex conductivity diagrams in the nearly free electron approximation

We investigate the possibility of the emergence of ultra-complex conductivity diagrams in the nearly free electron approximation for metals with cubic symmetry. Estimates show that the emergence of such diagrams requires the Fermi level to fall into very narrow energy intervals within the conduction band. In our view, this circumstance is mostly due to the high symmetry and the simplest analytical form of the dispersion relations $ε({\bf p})$ under consideration.