  Weyl semimetals with magnetic ordering provide a promising platform for the
investigation of rare topological effects such as the anomalous Hall effect,
resulting from the interplay of nontrivial bands with various spin
configurations. The materials $R$AlSi, where $R$ represents a rare-earth
element, are prominent representatives of Weyl semimetals, where the Weyl
states are induced by space inversion symmetry breaking and in addition, for
several rare-earth elements $R$, enhanced by time-reversal symmetry breaking
through the formation of a magnetic order at low temperature. We report optical
signatures of Weyl fermions in the magnetic compounds CeAlSi, PrAlSi, NdAlSi,
and SmAlSi as well as the non-magnetic family member LaAlSi by broad-frequency
infrared spectroscopy at room temperature, i.e., in the paramagnetic phase. A
similar profile of the optical conductivity spectrum and a metallic character
are observed for all compounds, with LaAlSi showing the strongest free charge
carrier contribution. Furthermore, the linear-in-frequency behavior of the
optical conductivity of all investigated compounds indicates the presence of
Weyl nodes in close vicinity of the Fermi energy, resulting from inversion
symmetry breaking in noncentrosymmetric structures. According to the
characteristics of these linear slopes, the $R$AlSi compounds are expected to
host mainly type-II Weyl states with overtilted Weyl cones. The results are
compared to the optical response of the closely related $R$AlGe materials,
which are considered as potential hybridization-driven Weyl-Kondo systems.
