  In Lorentz- and CPT-violating effective field theories involving scalar and
spinor fields, there exist forms of Lorentz violation that modify only the
scalar-spinor Yukawa interaction vertices. These affect low-energy fermion and
antifermion scattering processes through modifications to the nonrelativistic
Yukawa potentials. The modified potentials involve novel combinations of
momentum, spin, and Lorentz-violating background tensors.
