Non-trivial Berry phase and Shubnikov-de Haas oscillations in single-crystal Ni 3 Bi 2 Se 2

We present a comprehensive study of the electronic transport properties and first-principles calculations of ${\mathrm{Ni}}_{3}{\mathrm{Bi}}_{2}{\mathrm{Se}}_{2}$, a parkerite-structured compound, revealing its topological nodal-line semimetal behavior. Shubnikov-de Haas oscillations confirm the presence of Dirac-like fermions, supported by a nontrivial $\ensuremath{\pi}$-Berry phase, low effective mass (${m}^{*}\ensuremath{\sim}0.18\phantom{\rule{0.28em}{0ex}}{m}_{e}$), and a high Fermi velocity (${v}_{\mathrm{F}}\ensuremath{\sim}2.93\ifmmode\times\else\texttimes\fi{}{10}^{5}\phantom{\rule{0.28em}{0ex}}{\mathrm{ms}}^{\ensuremath{-}1}$). Weak-field magnetoconductivity exhibits a characteristic $\ensuremath{-}\mathrm{ln}$($B$) dependence, indicative of nodal-line features. The longitudinal resistivity fits well with the Bloch-Gruneisen-Mott model, pointing to multiple scattering mechanisms, including electron-phonon and Mott-interband. Hall effect and Boltzmann transport theory analyses suggest coexistence of electron and hole carriers. Density-functional theory calculations show a bulk band inversion between Ni-$d$ and Bi-$p$ orbitals without spin-orbit coupling, and the surface states merge into the bulk around 0.43 eV, further supporting the topologically nontrivial nature of ${\mathrm{Ni}}_{3}{\mathrm{Bi}}_{2}{\mathrm{Se}}_{2}$.