Fig. 1: Crystal structure and the negative magnetoresistance.

a, b Schematic drawings of a tilted type-II Dirac cone and a type-I Dirac cone, respectively. c Crystal structure of the type-II Dirac semi-metal PtSe2. The solid blue arrows present two equivalent a(b) axes. The purple arrow shows an axis a′ defined in normal to a. d Microscopic photo of a typical fabricated PtSe2 device with four-contact geometry. The dashed line highlights the sharp edges of the flake intersecting with an angle of 120°. Current and magnetic field are applied in parallel along the a axis indicated by the blue arrow. Scale bar: 2 μm. e Negative magnetoresistance \(\Delta \rho /\rho _0\) measured in the PtSe2 flakes with various thicknesses. Inset: Extracted chiral anomaly coefficient Cw with respect to the sample thickness. The error bars are the standard deviation and in some cases are smaller than the data point.