Fluctuation magnetoconductivity in Fe doped YBa2Cu3O7-delta sign change for B and I parallel to the planes

The magnetoconductivity in Fe doped YBa2Cu3O7-delta single crystals has been measured in the temperature region above T-c where superconducting fluctuations are known to be important. For small Fe concentrations and B parallel to c we obtain excellent agreement with accepted fluctuation theories. However, at higher Fe concentrations this description seems to break down. For B perpendicular to c we observe an anomalous dependence on the relative orientation of current and field, both applied along the ab-planes. For B parallel to I the magnetoconductivity is negative, as expected. For B perpendicular to I we observe a cross-over to a positive magnetoconductivity above about T-c + 10 K.