The generalization of spherical harmonics to vector-fields are the vector spherical harmonics [ https://en.wikipedia.org/wiki/Vector_spherical_harmonics ] .

I can provide simple code which relies on scipy's (scalar) spherical harmonics implementation and follows the same conventions to give vector spherical harmonics.

Could this be a nice-thing-to-have for scipy? A couple of scientific communities (astronomy, geodesy) use them a lot.