  Recognized as elementary particles in the standard model,Weyl fermions in
condensed matter have received growing attention. However, most of the
previously reportedWeyl semimetals exhibit rather complicated electronic
structures that, in turn, may have raised questions regarding the underlying
physics. Here, we report for the first time promising topological phases that
can be realized in specific honeycomb lattices, including ideal Weyl semimetal
structures, 3D strong topological insulators, and nodal-line semimetal
configurations. In particular, we highlight a novel semimetal featuring both
Weyl nodes and nodal lines. Guided by this model, we demonstrated that GdSI the
long perceived ideal Weyl semimetal has two pairs ofWeyl nodes residing at the
Fermi level, and that LuSI (YSI) is a 3D strong topological insulator with the
right-handed helical surface states. Our work provides a new mechanism to study
topological semimetals, and proposes a platform towards exploring the physics
of Weyl semimetals as well as related device designs.
