Ultrast study of Kondo-lattice coupling in the d-electron

We report our recent ultrafast optical measurements of the Zintl compound Yb$_{14}$MnSb$_{11}$, which was recently determined to be the first ferromagnetic Kondo lattice in the underscreened limit. The response at low temperatures to has two components, which we attribute to the underscreened nature of this Kondo system. In addition we measure the generation of coherent acoustic and optical phonons, that allow us to demonstrate a clear connection between the Kondo effect and lattice vibrations.