  Co2MnGe (CMG) has been demonstrated recently as a half-metallic ferromagnetic
Heusler alloy which possesses a topologically non-trivial band structure. This
behavior is unique to such systems and hence warrants extensive experimental
exploration for potential spintronic and chirality sensitive optoelectonic
applications. Here, we demonstrate that an epitaxial thin film of CMG acts as a
source of THz radiation upon photoexcitation by optical femtosecond laser
pulses. Detailed experiments have revealed that a large contribution to THz
emission occurs due to nonmagnetic or spin-independent origin, however,
significant contribution in the THz generation is evidenced through excitation
light helicity dependent circular photogalvanic effect (CPGE) confirming the
presence of topologically non-trivial carriers. Furthermore, we show that not
only the topological contribution is easily suppressed but also the overall THz
generation efficiency is also affected adversely for the epitaxial films grown
at high substrate temperatures.
