Intrinsic Chern Half-Metal with High Anomalous Hall Conductivity in 2D BaNiCl$_3$

Two-dimensional (2D) half-metals offer complete spin polarization at the Fermi level, making them candidates for dissipationless spin transport. Yet intrinsic 2D half-metals exhibiting robust topological features, particularly large Chern number anomalous Hall conductivities, remain exceptionally rare. Using first-principles calculations, we identify atomically thin BaNiCl$_3$, a layered halide perovskite (perovskene), as a topological half-metal. It exhibits a high Chern number ($C \ge 2$), a large anomalous Hall conductivity of 316~$\Omega^{-1},\mathrm{cm}^{-1}$, and a Fermi velocity of $\approx 0.78 \times 10^6$ m/s. The coexistence of complete spin polarization and high carrier velocity suggests low-dissipation spin transport. Spin-orbit coupling opens a sizable topological gap of $\sim 20\,$ meV, yielding nontrivial Berry curvature and enhancing the anomalous Hall response. Ferromagnetism is stabilized by the Ni$^{2+}$ ($d^8$) configuration and Cl-mediated superexchange, supporting magnetic ordering at elevated temperatures. These results establish BaNiCl$_3$ as a rare intrinsic Chern half-metal, with potential applications in quantum and spintronic technologies.