<p>Microstructures and thermal properties of solid alloys of the Bi–Ge system with a Ge content of 15.1 at.%, 40.8 at.%, 51.8 at.%, 70.3 at.%, and 85.4 at.% were investigated in the present study. Microstructural analysis was performed using scanning electron microscopy (SEM) combined with energy dispersive spectrometry (EDS). It was noticed that phase morphology of the primary germanium varies based on alloy composition from polygonal faceted to plate- and rod-like structures. Thermal diffusivity was measured by the xenon flash method in the temperature interval from 25&#xa0;°C to 150&#xa0;°C. The nearly constant thermal conductivity in the range of about 7 W·m⁻¹·K⁻¹ to 9 W·m⁻¹·K⁻¹ was observed over a wide compositional interval of Bi–Ge alloys, followed by its rapid increase with higher Ge content. Thermal conductivity of the studied alloys slightly decrease with the temperature increasing. Density dependence on composition at room temperature was determined using indirect Archimedean method. The obtained results from the alloy’s density measurements indicate the existence of a positive excess volume. Phase transition temperatures and latent heat of eutectic melting were measured using differential scanning calorimetry (DSC) and compared with the results of thermodynamic calculation based on the CALPHAD (calculation of phase diagram) method. Empirical equation for the estimation of the latent heat for Bi–Ge alloys was obtained.</p>