  HfTe5 is predicted to be a promising platform for studying topological
phases. Here through an electrical transport study, we present the first
observation of chiral anomaly and ultrahigh mobility in HfTe5 crystals.
Negative magneto-resistivity in HfTe5 is observed when the external magnetic
and electrical fields are parallel (B//E) and quickly disappears once B
deviates from the direction of E. Quantitative fitting further confirms the
chiral anomaly as the underlying physics. Moreover, by analyzing the
conductivity tensors of longitudinal and Hall traces, ultrahigh mobility and
ultralow carrier density are revealed in HfTe5, which paves the way for
potential electronic applications.
