  Magnetic, transport, and specific heat measurements have been performed on
layered metallic oxide Na$_{1.5}$Co$_2$O$_4$ as a function of temperature $T$.
Below a characteristic temperature $T^*$=30$-$40 K, electrical resistivity
shows a metallic conductivity with a $T^2$ behavior and magnetic susceptibility
deviates from the Curie-Weiss behavior showing a broad peak at $\sim$14 K. The
electronic specific heat coefficient $\gamma$ is $\sim$60 mJ/molK$^2$ at 2 K.
No evidence for magnetic ordering is found. These behaviors suggest the
formation of mass-enhanced Fermi liquid ground state analogous to that in
$d$-electron heavy fermion compound LiV$_2$O$_4$.
