Electrical and thermal transport properties of the substituted defect manganese silicides Mn$_{1-x-y}$Cr$_{x}$Ru$_{y}$Si$_{\delta \sim 1.74}$

Crystallizing in the TiSi$_{2}$ structure with considerable amount of random vacancies at the Si site, defect manganese silicides MnSi$_{\delta }(\delta \quad \sim $ 1.72-1.74) are unusual in many respects. One of them is their structural stability which is determined by the electron concentration. In addition, MnSi$_{\delta }$ is known for unusually low thermal conductivity $\sim $ 3 - 3.5 W/m K at 300 K. We have substituted MnSi$_{\delta }$ with Cr and Ru simultaneously and studied the electrical and thermal transport properties of the resulting alloys. Both resistivity and Seebeck coefficient are less sensitive to substitutions and maintain robust values as high as that of MnSi$\sim _{1.74}$. Hall measurements indicate that the carrier concentration remains high around 10$^{21}$/cm$^{3}$ and more or less same for all compositions. Thermal conductivity is decreased further and interestingly increases with T reaching values $\sim $ 2.5 W/m K at 300 K. These results will be presented and discussed.