The paper reports novel proton-conducting composites in the Ba2In2O5-Ba2InTaO6 eutectic oxide system. The samples were prepared in situ by solid state reaction method; their microstructural, thermal and electrical properties were investigated. The results show an essential conductivity enhancement of the (1-x)Ba2In2O5-xBa2InTaO6 samples both in dry and wet conditions compared with those for Ba2In2O5 and Ba2InTaO6 phases. The effect is maximal (near 2 orders of magnitude) for the composites with x = 0.2, 03, which retain a possibility to a water uptake and demonstrate the predominantly proton conduction at temperatures below 500 degrees C in wet air. (C) 2017 Elsevier B.V. All rights reserved.