The invention relates to crystalline nanometric olivine-type LiFe1-xMxPO4 powder with M being Co and/or Mn, and 0≦x≦1, with small particle size and narrow particle size distribution. A direct precipitation process is described, comprising the steps of: providing a water-based mixture having at a pH between 6 and 10, containing a dipolar aprotic additive, and Li(I), Fe(II), P(V), and Co(II) and/or Mn(II) as precursor components; heating said water-based mixture to a temperature less than or equal to its boiling point at atmospheric pressure, thereby precipitating crystalline LiFe1-xMxPO4 powder. An extremely fine particle size is obtained of about 80 nm for Mn and 275 nm for Co, both with a narrow distribution.