Fermi-surface reconstruction involving two van Hove singularities across the antiferromagnetic transition in BaFe2As2

► We study the kz-dispersion of BaFe2As2 using low-energy angle-resolved photoemission. ► A saddle-point dispersion at Z was observed below EF for the first time. ► Specifically strong eight-fold renormalization was identified around Z saddle point. ► Two van Hove singularities are involved in antiferromagnetic phase transition. ► Saddle-point instabilities are suggested as underlying fluctuation in iron-pnictides.