Electrical transport in

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Abstract
We report a systematic study of the effect of increasing oxygen deficiency on the electrical resistivity, tunnelling conductance and thermopower of . Stoichiometric behaves like a normal metal with a positive temperature coefficient of resistivity (TCR) and a negative thermopower which is proportional to temperature over the range 5 K-300 K. As the oxygen deficiency increases, the electrical resistivity shows a minimum at low temperature which progressively shifts to higher temperature with increasing . In the low-temperature limit the correction to the electrical conductivity follows a power-law behaviour with an exponent . We also find a cusp-like dip in the tunnelling conductance near zero bias voltage. We attribute both of these behaviours to enhanced interaction between the charge carriers in the system occurring because of the disorder. The thermopower of the oxygen-deficient samples is found to vary systematically with , showing a sign reversal at low temperature.