Fig. 4: A comparison of band isotropy among various 3D Dirac/Weyl materials.

A factor \(I=1-\left|\Delta v\right|/{v}_{{{\rm{F}}}{||}}\) is defined to describe the isotropy extent of 3D Dirac/Weyl materials. The more isotropic the band, the closer this factor approaches 1; conversely, the closer it approaches 0. The materials are listed where Fermi velocities along different directions have been probed in experiments. The isotropy factor of LaAlSi reaches 0.997.