Diminution of the thermal conductivity is a crucial aspect in thermoelectric research. We report a systematic and significant reduction of the cross-plane thermal conductivity in a model system consisting of DC sputtered TiNiSn and HfNiSn half-Heusler superlattices. The reduction of $\kappa$ is measured by the 3$\omega$ method and originates from phonon scattering at the internal interfaces. Heat transport in the superlattices is calculated based on Boltzmann transport theory, including a diffusive mismatch model for the phonons at the internal interfaces. Down to superlattice periodicity of 3 nm the phonon spectrum mismatch between the superlattice components quantitatively explains the reduction of $\kappa$. For very thin individual layers the interface model breaks down and the artificial crystal shows an enhanced $\kappa$. We also present an enhanced ZT value for all investigated superlattices compared to the single TiNiSn and HfNiSn films.Comment: 5 pages, 4 figures plus supplementary data with one additional figur

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RapidResearch Letter values for thin films in air were calculated to be 0.04 and 0.05 at 640 K and 1260 K, respectively. The value at 640 K is more than three times higher than observed for bulk samples at comparable temperatures (Fig. 2e).

Molecular beam epitaxy was used to deposit single crystal thin film Fe 1−x Ga x samples on ZnSe buffer layers grown on ͑001͒ and ͑110͒ single crystal GaAs substrates. The crystal quality of the GaAs surface and each deposited layer was monitored in situ by reflection high energy electron diffraction. The magnetic properties of the samples were characterized by vibrating sample magnetometry and ferromagnetic resonance ͑FMR͒. The FMR linewidth increases dramatically with Ga concentration while the cubic anisotropy term K 1 switches sign.