  The electron-doped cuprate Pr(2-x)Ce(x)CuO(4) is investigated using infrared
magneto-optical measurements. The optical Hall conductivity sigma_{xy} shows a
strong doping, frequency and temperature dependence consistent with the
presence of a temperature and doping-dependent coherent backscattering
amplitude which doubles the electronic unit cell. The data suggest that the
coherent backscattering vanishes at a quantum critical point inside the
superconducting dome and is associated with the commensurate antiferromagnetic
order observed by other workers. Using a spectral weight analysis we have
further investigated the Fermi-liquid like behavior of the overdoped sample.
The observed Hall-conductance spectral weight is about 10 times less than that
predicted by band theory, raising the fundamental question concerning the
effect of Mott and antiferromagnetic correlations on the Hall conductance of
strongly correlated materials.
