  We present a study on magnetotransport in films of the topological Dirac
semimetal Cd$_{3}$As$_{2}$ doped with Sb grown by molecular beam epitaxy. In
our weak antilocalization analysis, we find a significant enhancement of the
spin-orbit scattering rate, indicating that Sb doping leads to a strong
increase of the pristine band-inversion energy. We discuss possible origins of
this large enhancement by comparing Sb-doped Cd$_{3}$As$_{2}$ with other
compound semiconductors. Sb-doped Cd$_{3}$As$_{2}$ will be a suitable system
for further investigations and functionalization of topological Dirac
semimetals.
