  It was recently discovered that, depending on their symmetries, collinear
antiferromagnets can actually break the spin degeneracy in momentum space, even
in the absence of spin-orbit coupling. Such systems, recently dubbed
altermagnets, are signalled by the emergence of a spin-momentum texture set
mainly by the crystal and magnetic structure, relativistic effects playing a
secondary role. Here we consider all collinear $q$=0 antiferromagnetic
compounds in the MAGNDATA database allowing for spin-split bands. Based on
density-functional calculations for the experimentally reported crystal and
magnetic structures, we study more than sixty compounds and introduce numerical
measures for the average momentum-space spin splitting. We highlight some
compounds that are of particular interest, either due to a relatively large
spin splitting, such as CoF$_2$ and FeSO$_4$F, or because of their low-energy
electronic structure. The latter include LiFe$_2$F$_6$, which hosts nearly flat
spin-split bands next to the Fermi energy, as well as RuO$_2$, CrNb$_4$S$_8$,
and CrSb, which are spin-split antiferromagnetic metals.
