Coating the members of the olivine family LiMPO4 with conductive carbon is difficult, excepted in the case MFe. To overcome this difficulty, we found possible to coat LiMnPO4 with a thin layer of LiFePO4 to take benefit of the catalytic reaction of Fe with C, so that a 3nm-thick layer of carbon can be deposited at the surface of this composite. We find that the electrochemical properties of the carbon-coated LiFePO4–LiMnPO4 composite are improved with respect to the carbon-coated LiMn2/3Fe1/3PO4 solid solution with comparable Fe/Mn ratio. Therefore, the use of a LiFePO4 as a buffer layer between the high-density cathode element (like LiMnPO4) and the carbon layer opens a new route to improve the performance of the olivine family as the active element of the cathode for Li-ion batteries.