  Exotic massless fermionic excitations with non-zero Berry flux, other than
Dirac and Weyl fermions, could exist in condensed matter systems under the
protection of crystalline symmetries, such as spin-1 excitations with 3-fold
degeneracy and spin-3/2 Rarita-Schwinger-Weyl fermions. Herein, by using ab
initio density functional theory, we show that these unconventional
quasiparticles coexist with type-I and type-II Weyl fermions in a family of
transition metal silicides, including CoSi, RhSi, RhGe and CoGe, when the
spin-orbit coupling (SOC) is considered. Their non-trivial topology results in
a series of extensive Fermi arcs connecting projections of these bulk
excitations on side surface, which is confirmed by (010) surface electronic
spectra of CoSi. In addition, these stable arc states exist within a wide
energy window around the Fermi level, which makes them readily accessible in
angle-resolved photoemission spectroscopy measurements.
