Fermi surfaces are basic objects in solid state physics and in the spectral
theory of periodic operators. We define several measures connected to Fermi
surfaces and study their measure theoretic properties. From this we get absence
of singular continuous spectrum and of singular continuous components in the
density of states for symmetric periodic elliptic differential operators acting
on vector bundles. This includes Schroedinger operators with periodic magnetic
field and rational flux, as well as the corresponding Pauli and Dirac-type
operators.Comment: 19 page