Extremely large magnetoresistance and ultrahigh mobility in the topological Weyl semimetal candidate NbP

Recent experiments have revealed spectacular transport properties in semimetals, such as the large, non-saturating magnetoresistance exhibited by WTe2 (ref.1). Topological semimetals with massless relativistic electrons have also been predicted(2) as three-dimensional analogues of graphene(3). These systems are known as Weyl semimetals, and are predicted to have a range of exotic transport properties and surface states(4-7), distinct from those of topological insulators(8,9). Here we examine the magneto-transport properties of NbP, a material the band structure of which has been predicted to combine the hallmarks of a Weyl semimetal(10,11) with those of a normal semimetal. We observe an extremely large magnetoresistance of 850,000% at 1.85 K (250% at room temperature) in a magnetic field of up to 9 T, without any signs of saturation, and an ultra-high carrier mobility of 5 x 10(6) cm(2) V-1 s(-1) that accompanied by strong Shubnikov-de Haas (SdH) oscillations. NbP therefore presents a unique example of a material combining topological and conventional electronic phases, with intriguing physical properties resulting from their interplay.