  Superconducting films in perpendicular magnetic field are found to rectify
alternating currents. The effect has been observed both in plain and
nanostructured superconducting films (niobium and lead). The rectified voltage
appears both along and transverse to alternating current and strongly depends
on the magnetic field. Rectification phenomena is based on the property of
superconductors to have permanent circulating currents in magnetic field
(vortices) and to develop electric fields at high enough currents. In contrast
to previous findings, at higher current frequencies no asymmetric pinning sites
are needed to produce rectification and related guided flux motion.
