  We investigate an unconventional topological phase transition that occurs in
quantum spin Hall (QSH) systems when applying an external in-plane magnetic
field. We show that this transition between QSH and trivial insulator phases is
separated by a stable topological gapless phase, which is protected by the
combination of particle-hole and reflection symmetries, and thus, we dub it as
crystalline Weyl semimetal. We explore the stability of this new phase when
particle-hole symmetry breaking terms are present. Especially, we predict a
robust unconventional topological phase transition to be visible for materials
described by Kane and Mele model even if particle-hole symmetry is
significantly broken.
