Doping effect on the anomalous behavior of the Hall effect in   electron-doped superconductor Nd$_{2-x}$Ce$_x$CuO$_{4+\delta}$
  Transport properties of Nd$_{2-x}$Ce$_x$CuO$_{4+\delta}$ single crystal films are investigated in magnetic fields $B$ up to 9T at $T$=(0.4-4.2)K. An analysis of normal state (at $B>B_{c2}$) Hall coefficient $R_H$$^n$ dependence on Ce doping takes us to a conclusion about the existence both of electron-like and hole-like contributions to transport in nominally electron-doped system. In accordance with $R_H$$^n$(x) analysis an anomalous sign reversal of Hall effect in mixed state at $B<B_{c2}$ may be ascribed to a flux-flow regime for two types of carriers with opposite charges. 
T. B. Charikova, N. G. Shelushinina, G. I. Harus, D. S. Petukhov, A.   V. Korolev, V. N. Neverov, A. A. Ivanov
cond-mat.supr-con