We determine defining equations for the set of concise tensors minimal border rank in $${\mathbb {C}}^m{\mathord { \otimes } }{\mathbb {C}}^m$$ when $$m=5$$ and $$1_*$$ -generic $$m=5,6$$ . solve classical problem algebraic complexity theory classifying special case Our proofs utilize two recent developments: 111-equations defined by Buczyńska–Buczyński results Jelisiejew–Šivic on variety commu...