  A van der Waals coupled Weyl semimetal material NbIrTe4 is investigated by
combining scanning tunneling microscopy/spectroscopy and first principles
calculations. We observe a sharp peak in the tunneling conductance near the
zero bias energy, and its origin is ascribed to a van Hove singularity
associated with a Lifshitz transition of the topologically none trivial Fermi
arc states. Furthermore, tunneling spectroscopy measurements show a
surprisingly large signature of electron boson coupling, which presumably
represents anomalously enhanced electron phonon coupling through the enhanced
charge susceptibility. Our finding in van der Waals coupled material is
particularly invaluable due to applicable exfoliation technology for searching
exotic topological states by further manipulating near Fermi energy van Hove
singularity in nanometer scale flakes and their devices.
