Origin of the extremely large magnetoresistance in topological semimetal PtS n 4

$\mathrm{PtS}{\mathrm{n}}_{4}$ with extremely large magnetoresistance (XMR), a fascinating topological material platform, hosts a novel topological structure and Dirac node arcs, in which the Dirac nodes form closed loops in the momentum space. Here we performed the angular dependent magnetoresistivity (AMR), Hall effect, heat capacity measurements, and first-principles calculations to study the electronic properties of topological semimetal $\mathrm{PtS}{\mathrm{n}}_{4}$. There are some interesting observations on $\mathrm{PtS}{\mathrm{n}}_{4}$. (1) In the different experimental probes, we observed the anomalies around $T\ensuremath{\sim}55\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. Significant changes of the transport results and the heat capacity have been observed, indicating successive Fermi surface reconstruction induced by the temperature. It means there is Lifshitz transition (LT) induced by the temperature in $\mathrm{PtS}{\mathrm{n}}_{4}$. (2) The perfect compensation between the electron and hole has been found around $T\ensuremath{\sim}30\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, where the XMR appears, which is confirmed by the Hall effect measurements and the first-principles calculations. The XMR effect in $\mathrm{PtS}{\mathrm{n}}_{4}$ is suggested to originate from the combination of the electron-hole compensation and a particular orbital texture on the electron pocket. Meanwhile, we also found that LT seems to serve as a knob for the novel topological properties in two-dimensional (2D) topological semimetals (TSMs).