  We present a prediction of chiral topological metals with several classes of
unconventional quasiparticle fermions in a family of SrGePt-type materials in
terms of first-principles calculations. In these materials, fourfold spin-3/2
Rarita-Schwinger-Weyl (RSW) fermion, sixfold excitation, and Weyl fermions
coexist around the Fermi level as spin-orbit coupling is considered, and the
Chern number for the first two kinds of fermions is the maximal value four. We
found that large Fermi arcs from spin-3/2 RSW fermion emerge on the
(010)-surface, spanning the whole surface Brillouin zone. Moreover, there exist
Fermi arcs originating from Weyl points, which further overlap with trivial
bulk bands. In addition, we revealed that the large spin Hall conductivity can
be obtained, which attributed to the remarkable spin Berry curvature around the
degenerate nodes and band-splitting induced by spin-orbit coupling. Our
findings indicate that the SrGePt family of compounds provide an excellent
platform for studying on topological electronic states and the intrinsic spin
Hall effect.
