  We report on the single crystal growth and transport properties of a
topological semimetal CaAgBi which crystallises in the hexagonal $ABC-$type
structure with the non-centrosymmetric space group $\mathit{P6_3mc}$ (No. 186).
The transverse magnetoresistance measurements with current in the basal plane
of the hexagonal crystal structure reveal a value of about 30 % for I //
[10-10] direction and about 50 % for I // [1-210] direction at 10 K in an
applied magnetic field of 14 T. The magnetoresistance shows a cusp-like
behavior in the low magnetic-field region, suggesting the presence of weak
antilocalization effect for temperatures less than 100 K. The Hall measurements
reveal that predominant charge carriers are $p$ type exhibiting a linear
behavior for fields up to 14 T and can be explained based on the single band
model. The magnetoconductance of CaAgBi is analysed based on the modified
Hikami-Larkin-Nagaoka (HLN) model. Our first-principles calculations within a
density-functional theory framework reveal that CaAgBi supports a topological
Dirac semimetal state with Dirac points located on the rotational axis slightly
above the Fermi level and are protected by $C_{6v}$ point-group symmetry. The
Fermi surface consists of both the electron and hole pockets. However, the size
of hole pockets is much larger than electron pockets suggesting the dominant
$p$ type carriers in accord with our experimental results.
