  Antiferromagnets (AFMs) attract much research interest because of their
potential for spintronic applications and open fundamental physics questions.
Especially non-collinear AFMs (nAFMs) remain relatively unexplored. Here we
formulate the injection, transport, thermal and coherent pumping of spins in
nAFMs|normal metal bilayers, reporting that the spin current polarization is a
vector with components along both the N\'{e}el vector and net magnetic moment.
The interface spin conductance that governs spin injection and pumping is a
tensor and depends strongly on the local spin configuration. We explain
non-local spin transport experiments in hematite, attribute the controversial
sign problem of the antiferromagnetic spin Seebeck effect to interface effects,
and suggest that interface engineering may enhance the spin pumping efficiency.
