  Conductance fluctuations have been observed in macroscopic, quasi 3D PbTe
wide quantum wells. A significant increase of the correlation field occurs in a
temperature range from 40 mK to 1.2K. At the same time the fluctuation
amplitude stays near e^2/h although the lateral sample size is two orders of
magnitude larger than any typical length scale of diffusive electron transport.
We interpret this behavior in terms of phasecoherent electrontransport, which
takes advantage of a dramatic enhancement of the phasecoherence length of
electrons in edgechannels and edge channel loops in the bulk region.
