  Thermodynamic and transport measurements on NaxCoO2 (x ~ 0.7-0.75) over a
wide temperature range reveal a strongly enhanced low energy excitation
spectrum. The zero-field specific heat and resistance at low temperature are
proportional to T^n with n<1, in sharp contrast to behavior found in ordinary
Landau Fermi-liquid metals. For temperatures below ~5 K this unusual excitation
seen in the specific heat is partially suppressed in a magnetic field,
following a T/B scaling. The specific heat reduction at low T is partially
compensated by an increase at higher temperature. A quantitative comparison
with the magnetoresistance and the thermopower indicates that the low- energy
electronic state requires a description beyond the single band model.
