  We report on transport features in heavily boron doped nanocrystalline
diamond (BNCD) films which are not seen in conventional (s-wave) granular
superconductors. Observations include an anomalous resistance peak near to the
superconducting transition temperature as well as a strong zero bias
conductance peak in the current-voltage spectra. The effect of finite bias
current on the evolution of the resistance peak is systematically investigated
in this system. The shape of the resistance-temperature curves near the
critical temperature is seen to be strongly influenced by both magnetic field
and bias current. As the bias current is lowered the resistance peak becomes
more pronounced whereas when the magnetic field is varied the peak shifts
towards lower temperatures, the resistance upturn shows a quadratic temperature
dependence as expected for a Kondo transition. We find that a number of
transport features such as resistance peak height, zero bias conduction peak
height and width as well as magnetoresistance peaks scale according to a power
law dependence. We interpret these features as a result of a charge-Kondo
effect where hole dopants act as degenerate Kondo impurities by opening
additional pseudo-spin scattering channels.
