Spin-half Heisenberg antiferromagnet on a symmetric sawtooth chain: rotation-invariant Green’s functions and high-temperature seriesTaras Hutak, Taras Krokhmalskii, Oleg Derzhko and Johannes RichterEur. Phys. J. B, 96 4 (2023) 50DOI: https://doi.org/10.1140/epjb/s10051-023-00521-2