  The pairing mechanism in the iron-pnictide superconductors is still unknown.
However, similarities to the cuprate high-temperature superconductors suggest
that a similar mechanism may be at work. Recently, careful experimental studies
of the spin excitation spectrum revealed, like in the cuprates, a strong
temperature dependence in the normal state and a resonance feature in the
superconducting state. Motivated by these findings, we develop a model of
electrons interacting with a temperature dependent magnetic excitation spectrum
based on these experimental observations. We apply it to analyse angle resolved
photoemission and tunnelling spectra in Ba{1-x}KxFe2As2. We reproduce in
quantitative agreement with experiment a renormalisation of the quasiparticle
dispersion both in the normal and the superconducting state, and the dependence
of the quasiparticle linewidth on binding energy. We estimate the strength of
the coupling between electronic and spin excitations. Our findings support the
possibility of a pairing mechanism based dominantly on such a coupling.
