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 Ni₃Bi₂Se₂, 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 -Berry phase, low effective mass (m^*0. 180. 28em{0ex}m₄), and a high Fermi velocity (v₅2. 9310^50. 28em{0ex}ms^-1). Weak-field magnetoconductivity exhibits a characteristic -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 Ni₃Bi₂Se₂.