  Discovery of Weyl fermions in semimetallic tansition-metal monopnictides is a
major breakthrough in condensed matter physics. A Weyl semimetal is
characterized by the existence of robust Weyl points and unclosed topological
surface states in the form of Fermi arc. All the four compounds of the Weyl
semimetal transition monopnictide family i.e. NbP, TaP, NbAs and TaAs exhibit
extremely high mobility and unsaturated high magnetoresistance (MR). For
example, MR values are 8.5x10^5% at 1.85 K for NbP and 1.5x10^5% at 3 K in 9 T
for TaAs. NbP also achieves very low value of residual resistivity 0.63
micro-ohm cm at 2 K due to suppression of scattering resulting in ultra-high
mobility 5x10^6 cm^2/Vs, Interestingly, we find that the mobility of these
compounds play an important role for such a large MR.
