  We report a comprehensive study of magnetotransport properties,
angle-resolved photoemission spectroscopy (ARPES), and density functional
theory (DFT) calculations on self-flux grown LaAuSb$_2$ single crystals.
Resistivity and Hall measurements reveal a charge density wave (CDW) transition
at 77 K. MR and de Haas-Van Alphen (dHvA) measurements indicate that the
transport properties of LaAuSb$_2$ are dominated by Dirac fermions that arise
from Sb square nets. ARPES measurements and DFT calculations reveal an
electronic structure with a common feature of the square-net-based topological
semimetals, which is in good agreement with the magnetotransport properties.
Our results indicate the coexistence of CDW and Dirac fermion in LaAuSb$_2$,
both of which are linked to the bands arising from the Sb-square net,
suggesting that the square net could serve as a structural motif to explore
various electronic orders.
