  Klein tunneling is an old topic in relativistic quantum physics, and has been
observed recently in graphene where massless particles reside. Here, we propose
a new heterostructure platform for Klein tunneling to occur, which consists of
a Weyl-semimetal-based normal state/superconductor (NS) junction. By developing
a Blonder-Tinkham-Klapwijk-like theory, we find that Klein tunneling occurs at
normal incidence, which can lead to differential conductance doubling. If the
(single) Weyl semimeltals are replaced by double Weyl semimetals, anti-Klein
tunneling will take place of Klein tunneling. Our work provides a theoretical
guide for the detection of (anti-)Klein tunneling in three-dimensional chiral
NS junctions.
