The Weyl semimetal NbP was found to exhibit topological Fermi arcs and exotic magnetotransport properties. Here, we report on magnetic quantum-oscillation measurements on NbP and construct the three-dimensional Fermi surface with the help of band-structure calculations. We reveal a pair of spin-orbit-split electron pockets at the Fermi energy and a similar pair of hole pockets, all of which are strongly anisotropic. The Weyl points that are located in the k(z) approximate to pi/c plane are found to exist 5 meV above the Fermi energy. Therefore, we predict that the chiral anomaly effect can be realized in NbP by electron doping to drive the Fermi energy to the Weyl points

The layered ternary compound TaIrTe4 has been predicted to be a type-II Weyl semimetal with only four Weyl points just above the Fermi energy. Performing magnetotransport measurements on this material we find that the resistivity does not saturate for fields up to 70 T and follows a ρ ∼ B 1.5 dependence. Angular-dependent de Haas-van Alphen (dHvA) measurements reveal four distinct frequencies. Analyzing these magnetic quantum oscillations by use of density functional theory (DFT) calculations we establish that in TaIrTe4 the Weyl points are located merely ∼ 40-50 meV above the chemical potential, suggesting that the chemical potential can be tuned into the four Weyl nodes by moderate chemistry or external pressure, maximizing their chiral effects on electronic and magnetotransport properties.A recent conceptual breakthrough in the theory and classification of metals is the discovery of Weyl semimetals [1][2][3]. These semimetals have a topologically nontrivial electronic structure with fermionic Weyl quasiparticles -massless chiral fermions that play as well a fundamental role in quantum field theory and high-energy physics [4]. A consequence is that in Weyl semimetals topologically protected surface states appear in the form of Fermi lines that connect Weyl points (WPs) of opposite chirality, commonly referred to as Fermi arcs.Last year it was discovered that actually two types of Weyl fermions may exist in solids [5]. Weyl semimetals of type-I have a point-like Fermi surface and consequently zero density of states at the energy of WPs [6][7][8][9][10][11][12][13][14][15][16][17][18]. This is very different from Weyl semimetals of type-II [5,19], which have thermodynamic density of states at the energy of Weyl nodes and acquire exotic Fermi surfaces: in type-II systems Weyl nodes appear at touching points between electron and hole pockets. The presence of these very peculiar states is predicted to strongly affect magnetotransport properties of a Weyl semimetal and causes the conduction of electric current only in certain directions in presence of a magnetic field [5,20,21]. In spite of the considerable progress made by theory, only a handful of type-II Weyl semimetals have been identified on the basis of electronic band-structure calculations: WTe 2 , MoTe 2 , Ta 3 S 2 , YbMnBi 2 and, very recently, TaIrTe 4 [5,16,[22][23][24][25].Of interest is in particular the orthorhombic ternary compound TaIrTe 4 as it combines structural simplicity with topological WPs: TaIrTe 4 is a structurally layered material which hosts just four type-II WPs, the minimal number of WPs a system with time-reversal invariance can host [22]. Moreover, the WPs are well separated from each other in momentum space. Such a large momentum-space separation promises a strong impact of the Weyl fermions on the transport properties. Indeed, we present in this Letter magnetotransport and magnetic quantum oscillations studies of TaIrTe 4 that evidence a non-saturating magnetoresistance signaling the presence of Weyl nodes. Analyzing de Haas-van Alp...

Weyl and Dirac fermions have created much attention in condensed matter physics and materials science. Recently, several additional distinct types of fermions have been predicted. Here, we report ultra-high electrical conductivity in MoP at low temperature, which has recently been established as a triple point fermion material. We show that the electrical resistivity is 6 nΩ cm at 2 K with a large mean free path of 11 microns. de Haas-van Alphen oscillations reveal spin splitting of the Fermi surfaces. In contrast to noble metals with similar conductivity and number of carriers, the magnetoresistance in MoP does not saturate up to 9 T at 2 K. Interestingly, the momentum relaxing time of the electrons is found to be more than 15 times larger than the quantum coherence time. This difference between the scattering scales shows that momentum conserving scattering dominates in MoP at low temperatures.