  Adler-Bell-Jackiw chiral anomaly is a representative feature arising from the
topological nature in topological semimetal. We report the first experimental
observation of giant planar Hall effect in type-II Weyl semimetal WTe2. Our
comprehensive analyes of the experimental data demonstrate that the detected
planar Hall effect is originated from the chiral anomaly of Weyl fermions.
Unlike the somewhat elusive negative magnetoresistance, the planar Hall effect
is robust and easy to be detected in type-II Weyl semimetal. This work reveals
that the planar Hall effect is an effective transport probe to determine the
topological nature of topological semimetals, especially in type-II Weyl
semimetals.
