YNiSn${}_2$: A candidate Dirac semimetal

We report the synthesis and physical properties of the new compound YNiSn${}_2$, which crystallizes in the orthorhombic $\mathit{\text{Cmcm}}$ structure. The material exhibits semimetallic behavior and develops a giant positive magnetoresistance approaching 1200% at $B=16$ T. Pronounced de Haas-van Alphen and Shubnikov-de Haas oscillations reveal a dominant quasi-two-dimensional Fermi surface with an exceptionally small cyclotron effective mass of $m^{\ast }=0.08m0$, indicating light carriers and a tiny Fermi surface pocket. The strong anisotropy revealed by Shubnikov-de Haas quantum oscillation measurements highlights the low-dimensional electronic character of YNiSn${}_2$, positioning it as a promising Dirac semimetal candidate.