  We demonstrate the full thermoelectric and structural characterization of
individual bismuth-based (Bi-based) core/shell nanowires. The influence of
strain on the temperature dependence of the electrical conductivity, the
absolute Seebeck coefficient and the thermal conductivity of bismuth/titanium
dioxide ($\text{Bi}/\text{TiO}_{2}$) nanowires with different diameters is
investigated and compared to bismuth (Bi) and bismuth/tellurium (Bi/Te)
nanowires and bismuth bulk. Scattering at surfaces, crystal defects and
interfaces between the core and the shell reduces the electrical conductivity
to less than $5\,\%$ and the thermal conductivity to less than $25\,\%$ to
$50\,\%$ of the bulk value at room temperature. On behalf of a compressive
strain, $\text{Bi}/\text{TiO}_{2}$ core/shell nanowires show a decreasing
electrical conductivity with decreasing temperature opposed to that of Bi and
Bi/Te nanowires. We find that the compressive strain induced by the
$\text{TiO}_{2}$ shell can lead to a band opening of bismuth increasing the
absolute Seebeck coefficient by $10\,\%$ to $30\,\%$ compared to bulk at room
temperature. In the semiconducting state, the activation energy is determined
to $\left|41.3\pm0.2\right|\,\text{meV}$. We show that if the strain exceeds
the elastic limit the semimetallic state is recovered due to the lattice
relaxation.
