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Multiband superconductivity in AFe2As2, A = K, Rb, Cs

The compounds AFe2As2, where A = K, Rb, Cs, are a promising series to study superconductivity in iron pnictides. No chemical site disorder is introduced by dopants and the upper critical fields are easily accessible. We studied the structure of single crystals by four-circle x-ray diffraction, the phase diagram by thermal expansion and magnetostriction, and the Fermi surface via quantum oscillations observed in the magnetostriction. Despite considerable chemical pressure exerted on the structure, superconducting properties are surprisingly similar across the series. The strength of electronic correlations, however, increases.