Filling voids with rare earth atoms is an effective way to lowering thermal conductivity which necessarily enhances thermoelectric properties of skutterudite compounds. Yb atom is one of the most effective species among the rare earth atoms for filling the voids in the skutterudite structure due to a large atomic mass, radius and it is intermediate valence state. In this work, we aim to find the best filling partners for Yb using different combinations of Ce and In as well as to optimize actual filling fraction in order to achieve high values of ZT. The traditional method of synthesis relying on melting-annealing and followed by spark plasma sintering was used to prepare all samples. The thermoelectric properties of four samples of Yb0.2In0.2Co4Sb12, Yb0.2Ce0.15Co4Sb12. Yb0.2Ce0.15In0.2Co4Sb12, and Yb0.3Ce0.15In0.2Co4Sb12 (nominal) were examined based on the Seebeck coefficient, electrical conductivity, thermal conductivity, and Hall coefficient. Hall coefficient and Seebeck coefficient signs confirm that all samples are n-type skutterudite compounds. Carrier density increases with the increasing Yb + Ce content. A high power factor value of 57.7 mu W/K-2/cm for Yb0.2Ce0.15Co4Sb12 and a lower thermal conductivity value of 2.82 W/m/K for Yb0.2Ce0.15In0.2Co4Sb12 indicate that small quantities of Ce with In may be a good partner to Yb to reduce the thermal conductivity further and thus enhance the thermoelectric performance of skutterudites. The highest ZT value of 1.43 was achieved for Yb0.2Ce0.15In0.2Co4Sb12 triple-filled skutterudite at 800 K. (C) 2012 Elsevier Inc. All rights reserved.