Charge density wave and large non-saturating magnetoresistance in YNiC₂ and LuNiC₂

We report a study of physical properties of two quasi-low dimensional metals YNiC$_2$ and LuNiC$_2$ including the investigation of transport, magnetotransport, galvanomagnetic and specific heat properties. In YNiC$_2$ we reveal two subsequent transitions associated with the formation of weakly coupled charge density wave at $T_{CDW}$ = 318 K, and its locking in with the lattice at $T_1$ = 275 K. These characteristic temperatures follow the previously proposed linear scaling with the unit cell volume, demonstrating its validity extended beyond the lanthanide-based $R$NiC$_2$. We also find that, in the absence of magnetic ordering able to interrupt the development of charge density wave, the Fermi surface nesting leads to opening of small pockets, containing high mobility carriers. This effect gives rise to substantial enhancement of magnetoresistance, reaching 470 % for YNiC$_2$ and 50 % for LuNiC$_2$ at $T$ = 1.9 K and $B$ = 9 T.