The effect of heavy and light electronic bands on thermoelectric properties of Mg2Si1-xSnx alloys: Insights from an ab-initio study

•The electronic structure of Mg2Si1-xSnx compounds is studied in detail from first principles.•The transport parameters (S, σ, κe) of Mg2Si1-xSnx were elucidated.•The energy band gaps decrease with increasing Sn content in Mg2Si1-xSnx.•Heavy conduction band, CBH, and light conduction band, CBL, are formed in Mg2Si1-xSnx.•n-type Mg2Si1-xSnx compounds are found to be excellent TE materials for practical use.