  We report the specific heat, magnetic, magnetotransport and galvanomagnetic
properties of polycrystalline GdNiC$_2$. In the intermediate temperature region
above $T_N$ = 20 K, we observe large negative magnetoresistance due to Zeeman
splitting of the electronic bands and partial destruction of a charge density
wave ground state. Our magnetoresistance and Hall measurements show that at low
temperatures a magnetic field induced transformation from antiferromagnetic
order to a metamagnetic phase results in the partial suppression of the CDW.
