Layer-selective proximity symmetry breaking enables anomalous and nonlinear Hall responses in $1H$-Nb$X_2$ ($X =$ S, Se, Te)

Nonlinear Hall responses provide an electrical probe of Berry-curvature dipoles, but they are symmetry forbidden in many pristine two-dimensional metals. We show that layer-selective magnetic proximity provides a symmetry-controlled route to induce and tune anomalous and nonlinear Hall responses in