  Hybridization between the localized f-electrons and the delocalized
conduction electrons together with the crystal electric field (CEF) play a
determinant role in governing the many-body ground state of a
correlated-electron system. Here, we investigate the low-energy CEF states in
CeAg_2Ge_2, a prototype Kondo-lattice antiferromagnet where Kondo correlation
is found to exist within the antiferromagnetic phase. Using time-domain THz
reflection spectroscopy, we show the first direct evidence of two low-energy
CEF transitions at 0.6 THz (2.5 meV) and 2.1 THz (8.7 meV). The presence of
low-frequency infrared-active phonon modes further manifests as a Fano-modified
lineshape of the 2.1 THz CEF conductivity peak. The temporal spectral weights
obtained directly from the THz time traces, in addition, corroborate the
corresponding CEF temperature scales of the compound.
