Evidence of a structural phase transition in superconducting SmFeAsO(1-x)F(x) from 19F NMR.

We report resistivity, magnetization and (19)F NMR results in a polycrystalline sample of SmFeAsO(0.86)F(0.14). The resistivity and magnetization data show a sharp drop at 48 K indicating a superconducting transition. The nuclear spin-lattice rate (1/T(1)) and spin-spin relaxation rate (1/T(2)) clearly show the existence of a structural phase transition near 163 K in the sample, which also undergoes a superconducting transition. This finding creates interest in exploring whether this is unique for Sm based systems or is also present in other rare-earth based 1111 superconductors.