  In this paper, we report the intercone transport of Weyl fermions in NbAs
with external magnetic field in parallel to electric field, a quantum
phenomenon known as the Adler-Bell-Jackiw anomaly. Surprisingly, the resulting
negative magnetoresistance (MR) in NbAs shows significant difference from NbP.
The observed low-field positive MR dip, which is missing in NbP at low
temperatures, indicates that the spin-orbital coupling (SOC) is significantly
stronger in NbAs than in the former. The results imply that the contribution of
arsenic to SOC in TaAs and NbAs is not negligible.
