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Thermopower, resistivity, and heat capacity have been measured on eight Sn-substituted ${\mathrm{FeSb}}_{2\ensuremath{-}x}{\mathrm{Sn}}_{x}$ samples with $x=0--0.15$. A giant peak in the low temperature thermopower of ${\mathrm{FeSb}}_{2}$ is observed and is similar to what is found in the Kondo insulator $\mathrm{FeSi}$. The ab initio calculated band structure of ${\mathrm{FeSb}}_{2}$ shows striking similarities to that of $\mathrm{FeSi}$. For the samples with Sn substitution the data indicate that as the Sn content increases ${\mathrm{FeSb}}_{2\ensuremath{-}x}{\mathrm{Sn}}_{x}$ evolves from a Kondo insulator into a heavy fermion metal similar to what is observed for ${\mathrm{FeSi}}_{1\ensuremath{-}x}{\mathrm{Al}}_{x}$.

Temperature dependent synchrotron powder diffraction and single crystal neutron diffraction data are used for probing the vibrational states and disorder in type I clathrates ${\mathrm{Ba}}_{8}{\mathrm{Ga}}_{16}{\mathrm{Si}}_{30}$, ${\mathrm{Ba}}_{8}{\mathrm{Ga}}_{16}{\mathrm{Ge}}_{30}$, ${\mathrm{Ba}}_{8}{\mathrm{In}}_{16}{\mathrm{Ge}}_{30}$, and ${\mathrm{Sr}}_{8}{\mathrm{Ga}}_{16}{\mathrm{Ge}}_{30}$. If an empirical disorder term is included, the temperature dependence of the atomic displacement factors (ADPs) of the framework and guest atoms can be described by a Debye and Einstein model, respectively. None of the guest atoms in the large cages are located in the center and the vibrational frequencies $({\ensuremath{\theta}}_{\mathrm{E}})$ are of the order $80\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ or larger for all structures, in good agreement with theoretical predictions. Even though the Sr ADPs are larger than the Ba ADPs in all the clathrates, the data show that ${\ensuremath{\theta}}_{\mathrm{E}}$ of Sr in ${\mathrm{Sr}}_{8}{\mathrm{Ga}}_{16}{\mathrm{Ge}}_{30}$ is larger than for the Ba atoms. This is due to stronger guest-host chemical bonding in ${\mathrm{Sr}}_{8}{\mathrm{Ga}}_{16}{\mathrm{Ge}}_{30}$. Since ${\ensuremath{\theta}}_{\mathrm{E}}$ of Sr has been reported to be much smaller in the literature we have also measured the specific heat of ${\mathrm{Sr}}_{8}{\mathrm{Ga}}_{16}{\mathrm{Ge}}_{30}$ with ${\mathrm{Ba}}_{8}{\mathrm{Ga}}_{16}{\mathrm{Ge}}_{30}$ as a reference. It is found that localized excitations with a characteristic energy of approximately $35\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ exist in both compounds, however, the total number of states is too low to be associated with either tunneling states or localized vibration of each of the guest atoms.