  The spectrally resolved Terahertz photoconductivity between two separately
contacted edge-channels of a two-dimensional electron gas in the quantum Hall
regime is investigated. We use a not-simply-connected sample geometry which is
topologically equivalent to a Corbino disc. Due to the high sensitivity of our
novel sample structure, a weak resonance situated on the high energy side of
the well known cyclotron resonance is revealed. The magnetic field as well as
the carrier density dependence of this weak resonance, in comparison with
different models suggests that the additional resonance is an edge induced
magneto plasmon, which has so far not been observed in semiconductors.
