Large magnetoresistance and de Haas–van Alphen oscillations in the topological semimetal candidates BaX4 (X=Ga, In)

We report the magnetoresistance (MR), de Haas--van Alphen (dHvA) oscillations, and first-principles calculation studies on topological semimetal candidates ${\mathrm{Ba}X}_{4}$ $(X=\mathrm{Ga}, \mathrm{In})$. Large unsaturated MR that reaches $3\ifmmode\times\else\texttimes\fi{}{10}^{3}%$ in ${\mathrm{BaGa}}_{4}$ and $4\ifmmode\times\else\texttimes\fi{}{10}^{4}%$ in ${\mathrm{BaIn}}_{4}$ are observed, which is due to the carrier compensations and high mobility. Evident dHvA oscillations are detected with $B//[001]$ configuration, from which the quantum mobilities are extracted. The light cyclotron effective masses are extracted from the fitting of the thermal damping term in the LK formula. According to the first-principles calculations, ${\mathrm{Ba}X}_{4}$ possesses several Dirac points in the absence of spin-orbit coupling (SOC), some of which open negligible gaps when SOC is considered. The ${Z}_{2}$ invariants of ${\mathrm{Ba}X}_{4}$ are equal to 1, indicating the nontrivial topological properties.