  The recent discovery of magnetism within the family of exfoliatable van der
Waals (vdW) compounds has attracted considerable interest in these materials
for both fundamental research and technological applications. However current
vdW magnets are limited by their extreme sensitivity to air, low ordering
temperatures, and poor charge transport properties. Here we report the magnetic
and electronic properties of CrSBr, an air-stable vdW antiferromagnetic
semiconductor that readily cleaves perpendicular to the stacking axis. Below
its N\'{e}el temperature, $T_N = 132 \pm 1$ K, CrSBr adopts an A-type
antiferromagnetic structure with each individual layer ferromagnetically
ordered internally and the layers coupled antiferromagnetically along the
stacking direction. Scanning tunneling spectroscopy and photoluminescence (PL)
reveal that the electronic gap is $\Delta_E = 1.5 \pm 0.2$ eV with a
corresponding PL peak centered at $1.25 \pm 0.07$ eV. Using magnetotransport
measurements, we demonstrate strong coupling between magnetic order and
transport properties in CrSBr, leading to a large negative magnetoresistance
response that is unique amongst vdW materials. These findings establish CrSBr
as a promising material platform for increasing the applicability of vdW
magnets to the field of spin-based electronics.
