A new type of potassium niobium phosphate, K Nb P O , has been prepared and its structure has been determined by single crystal X-ray diffraction analysis. The results show that it crystallizes in a novel (3+1)-dimensional incommensurately modulated structure with a triclinic superspace group P-1(???)0 and modulation vector q = -0.35281a* + 0.17630b* + 0.25807c*. K Nb P O features a layer structure containing [K ]? layers, [K ]? layers and [Nb P O ]? layers alternatively staking along the c-axis.
