Large out-of-plane and linear in-plane magnetoresistance in layered hafnium pentatelluride

The prediction of the quantum spin Hall effect in two-dimensional $\mathrm{ZrT}{\mathrm{e}}₅$ and $\mathrm{HfT}{\mathrm{e}}₅$ monolayers has generated considerable recent interest in these materials. In addition, Dirac points and chiral-anomaly-induced negative longitudinal magnetoresistance (MR) have been observed in $\mathrm{ZrT}{\mathrm{e}}₅$. Herein, we study the transport behavior of $\mathrm{HfT}{\mathrm{e}}₅$ single crystals in detail and find a large $(0.9\ifmmode\times\else\texttimes\fi{}{10}⁴%)$ out-of-plane transverse MR, which is among the highest for layered materials reported thus far. We also encounter a large linear in-plane transverse (magnetic field $\ensuremath{\parallel}\phantom{\rule{0.16em}{0ex}}c$, current $\ensuremath{\parallel}\phantom{\rule{0.16em}{0ex}}a)$ MR and discuss its possible origin. The mass anisotropy $(\ensuremath{\gamma}=5.4$ at 125 K) obtained by scaling angle-dependent MR data is consistent with the $\mathrm{HfT}{\mathrm{e}}₅$ elliptical Fermi surface.