  Suppression of T_c in bilayer bismuth and thallium cuprates, by substitution
of Co impurities at Cu sites, are taken for examination. T_c suppression data
on differently doped Bi2212 and Tl2212 are analysed within the unitary
pair-breaking formalism due to Abrikosov and Gorkov, by fitting data points to
a phenomenological relation valid for weak coupling d-wave superconductors.
Values of the pseudogap magnitude at each doping are thereby estimated within a
"fermi-level density of states suppression" picture. Pseudogap magnitude from
our estimation is observed to have a correspondence with a related
characteristic temperature T^\star obtained by thermoelectric power
measurements. Effects of pseudogap, on the density of states, is studied by
calculating the susceptibility which shows a broad peak at high temperature.
This peak feature in susceptibility is indicative of an unusual metallic state
which could further be explored by systematic other measurements.
