Nanocomposites with a primary nanocrystalline SiC matrix and a secondary nanocrystalline Zn phase were synthesized in toroid-type cell, under pressure up to 8 GPa at temperature up to 1650^oC using high-pressure infiltration technique. The advantage of our technique is that in a single, continuos process (i) the powder is compressed to form the matrix with nanopores (ii) the nanopores are filled with a second phase (iii) the second phase, here Zn, crystallizes in the nano-scale. The key limitation of this technique is that the pores in the matrix need to stay open during the entire process of infiltration. We used SiC nanopowders with different granularity (particle size from several to hundreds of nanometers) and mean crystal size in the range 10 - 60 nm. The porosity studies of the green bodies prepared from the investigated powders (2 and 8 GPa, room temperature) showed that: (i) in all samples open porosity was maintained, (ii) in the powder with particle size in the range of several nanometers fractal structure of the powder promoted the infiltration process. The nanocomposites, which we have obtained showed microstructure with two phases distributed (mixed) homogeneously on the nano-scale. Process conditions and powder granularity influenced the crystal size of the second phase. The mean grain size of Zn varied from 20 to 100 nm and was smaller in the composites obtained with finer matrix, under higher pressure at lower temperature. The volume fraction of Zn reached 20 % independently of the powder morphology and p – T conditions. The strength and specific surface of the interfacial boundary influence the mechanical properties of the composites. The microhardness HV₀₂ of our nanocomposites varied from 5 to 16 GPa and rose up with an increase of pressure and temperature of the infiltration process and with the powder refinement.