  As a new type of fermions without counterpart in high energy physics, triply
degenerate fermions show exotic physical properties, which are represented by
triply degenerate nodal points in topological semimetals. Here, based on the
space group theory analysis, we propose a practical guidance for seeking a
topological semimetal with triply degenerate nodal points located at a
symmetric axis, which is applicable to both symmorphic and nonsymmorphic
crystals. By using this guidance in combination with the first-principles
electronic structure calculations, we predict a class of triply degenerate
topological semimetals RERh$_{6}$Ge$_{4}$ (RE=Y, La, Lu). In these compounds,
the triply degenerate nodal points are located at the $\Gamma$-A axis and not
far from the Fermi level. Especially, LaRh$_{6}$Ge$_{4}$ has a pair of triply
degenerate nodal points located very closely to the Fermi level. Considering
the fact that the single crystals of RERh$_{6}$Ge$_{4}$ have been synthesized
experimentally, the RERh$_{6}$Ge$_{4}$ class of compounds will be an
appropriate platform for studying exotic physical properties of triply
degenerate topological semimetals.
