  We explore Weyl and Dirac semimetals with tilted nodes as platforms for
realizing an intrinsic superconducting diode effect. Although tilting breaks
sufficient spatial and time-reversal symmetries, we prove that -- at least for
conventional $s$-wave singlet pairing -- the effect is forbidden by an emergent
particle-hole symmetry at low energies if the Fermi level is tuned to the
nodes. Then, as a stepping stone to the three-dimensional semimetals, we
analyze a minimal one-dimensional model with a tilted helical node using
Ginzburg-Landau theory. While one might naively expect a drastic enhancement of
the effect when the node turns from type-I to type-II, we find that the
presence of multiple Fermi pockets is more important as it enables multiple
pairing amplitudes with indepedent contributions to supercurrents in opposite
directions. Equipped with this insight, we construct minimal lattice models of
Weyl and Dirac semimetals and study the superconducting diode effect in them.
Once again, we see a substantial enhancement when the normal state has multiple
Fermi pockets per node that can accommodate more than one pairing channel. In
summary, this study sheds light on the key factors governing the intrinsic
superconducting diode effect in systems with asymmetric band structures and
paves the way for realizing it in topological semimetals.
