We report measurements of quasiparticle relaxation dynamics in the high-temperature superconductor (Ba,K)Fe$_{ 2}$As$_{ 2}$ in optimally doped, underdoped and undoped regimes. In the underdoped sample, spin-density wave (SDW) order forms at $\sim$85 K, followed by superconductivity at $\sim$ 28 K. We find the emergence of a normal-state order that suppresses SDW at a temperature $T^{ \ast} \sim$ 60 K and argue that this normal-state order is a precursor to superconductivity.
Categories: cond-mat.supr-con cond-mat.str-el