TaIrTe4: A ternary type-II Weyl semimetal

In metallic condensed matter systems two different types of Weyl fermions can in principle emerge, with either a vanishing (type-I) or with a finite (type-II) density of states at the Weyl node energy. So far only ${\mathrm{WTe}}_{2}$ and ${\mathrm{MoTe}}_{2}$ were predicted to be type-II Weyl semimetals. Here we identify ${\mathrm{TaIrTe}}_{4}$ as a third member of this family of topological semimetals. ${\mathrm{TaIrTe}}_{4}$ has the attractive feature that it hosts only four well-separated Weyl points, the minimum imposed by symmetry. Moreover, the resulting topological surface states---Fermi arcs connecting Weyl nodes of opposite chirality---extend to about 1/3 of the surface Brillouin zone. This large momentum-space separation is very favorable for detecting the Fermi arcs spectroscopically and in transport experiments.