${\mathrm{NbAl}}_3$ is a novel semimetal with a type-II Dirac node $\sim 230$ meV above the Fermi energy. We have performed both out-of-plane ($B\parallel c$) and in-plane magnetotransport measurements ($B\perp c$) on single-crystalline ${\mathrm{NbAl}}_3$. In our out-of-plane data, we observe an interesting linear component in the transverse magnetoresistance, and the mobility spectrum analysis of the out-of-plane data reveals an emergence of high-mobility electrons at low temperatures. Near $B\parallel c$, Shubnikov–de Haas oscillations are discerned in the magnetoresistance. The oscillation frequencies agree with the density functional theory calculation, the same theory that shows that the Dirac node is far above the Fermi energy. Therefore, the out-of-plane results cannot be attributed to the type-II Dirac node but suggest ${\mathrm{NbAl}}_3$ has additional Dirac or Weyl nodes close to the Fermi energy. To support this, we examine the in-plane data obtained with the magnetic field perpendicular to the tilting direction of the type-II Dirac cone. Such field direction excludes the possibility of chiral anomaly from the predicted type-II Dirac node. Remarkably, we observe the planar Hall effect, anisotropic magnetoresistance, and negative longitudinal magnetoresistance. These in-plane results are a strong indication of chiral anomaly unrelated to the previously established type-II Dirac node, pointing to the presence of additional Dirac or Weyl nodes near the Fermi energy. Our density functional theory calculation reveals a type-I Dirac node $\sim 50$ meV below the Fermi energy that has previously been overlooked. We argue that the exotic transport phenomena observed in ${\mathrm{NbAl}}_3$ can be attributed to this identified type-I Dirac node.

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• Fermi surface
• Dirac semimetal
• Single crystal materials
• Transport techniques