  Reading the magnetic state of antiferromagnetic (AFM) thin films is key for
AFM spintronic devices. We investigate the underlying physics behind the spin
Hall magnetoresistance (SMR) of bilayers of platinum and insulating AFM
hematite ({\alpha}-Fe2O3) and find an SMR efficiency of up to 0.1%, comparable
to ferromagnetic based structures. To understand the observed complex SMR field
dependence, we analyse the effect of misalignments of the magnetic axis that
arise during growth of thin films, by electrical measurements and direct
magnetic imaging, and find that a small deviation can result in significant
signatures in the SMR response. This highlights the care that must be taken
when interpreting SMR measurements on AFM spin textures.
