Flat-band physics in the spin-1/2 sawtooth chain Oleg Derzhko, Jürgen Schnack, Dmitry V. Dmitriev, Valery Ya. Krivnov and Johannes Richter Eur. Phys. J. B, 93 8 (2020) 161 Published online: 24 August 2020 DOI: 10.1140/epjb/e2020-10224-1