  Nonlinear Hall effect (NLHE) is a new type of Hall effect with wide
application prospects. Practical device applications require strong NLHE at
room temperature (RT). However, previously reported NLHEs are all
low-temperature phenomena except for the surface NLHE of TaIrTe4. Bulk RT NLHE
is highly desired due to its ability to generate large photocurrent. Here, we
show the spin-valley locked Dirac state in BaMnSb2 can generate a strong bulk
NLHE at RT. In the microscale devices, we observe the typical signature of an
intrinsic NLHE, i.e. the transverse Hall voltage quadratically scales with the
longitudinal current as the current is applied to the Berry curvature dipole
direction. Furthermore, we also demonstrate our nonlinear Hall device's
functionality in wireless microwave detection and frequency doubling. These
findings broaden the coupled spin and valley physics from 2D systems into a 3D
system and lay a foundation for exploring bulk NLHE's applications.
