Four new quaternary alkali neodymium thiophosphates KgNd[PS4](4) (1), K3Nd[PS4](2) (2), Cs3Nd[PS4](2) (3), and K3Nd3(PS4](4) (4) were synthesized by reacting Nd with in situ formed fluxes of K2S3 or Cs2S3, P2S5 and S in appropriate molar ratios at 973 K. Their crystal structures are determined by single crystal X-ray diffraction. Crystal data: 1: space group C2/c, a = 20.1894(16), b = 9.7679(5), c = 17.4930(15) angstrom, beta = 115.66(1)degrees, and Z = 4; 2: space group P2(1)/c, a = 9.1799(7), b = 16.8797(12), c 9.4828(7) angstrom, beta = 90.20(1)degrees, and Z = 4; 3: space group P2(1)/n, a = 15,3641(13), b = 6.8865(4), c = 15.3902(13) angstrom, beta = 99.19(1)degrees, and Z = 4; 4: space group C-2/c, a = 16.1496(14), b = 11.6357(7), c = 14.6784(11) angstrom, beta = 90.40(1)degrees, and Z = 4. The structure of 1 is composed of one-dimensional (infinity)(1)(Nd[PS4](4)}(9-) chains and charge balancing K+ ions. Within the chains, eight-coordinated Nd3+ ions, which are mixed with K+ ions, are connected by [PS4](3-) tetrahedra. The crystal structures of 2 and 3 are characterized by anionic chains (1)(infinity){Nd[PS4](2)}(3-) being separated by K+ or Cs+ ions. Along each chain the Nd3+ ions are bridged by [PS4](3-) anions. The difference between the structures of 2 and 3 is that in 2 the Nd3+ ions are coordinated by four edge-sharing [PS4](3-) tetrahedra while in 3 each Nd3+ ion is surrounded by one corner-sharing, one face-sharing, and two edge-sharing [PS4](3-) tetrahedra. The structure of 4 is a three-dimensional network with K+ cations residing in tunnels running along [110] and [(1) over bar 10]. The {Nd(1)S-8} polyhedra share common edges with four [PS4] tetrahedra forming one-dimensional chains (1)(infinity){Nd[PS4](2)}(3-) running along [110] and [(1) over bar 10]. The chains are linked by {Nd((2))S-8} polyhedra yielding the final three-dimensional network (3)(infinity)(Nd[PS4](2)}(3-). The internal vibrations of both crystallographically independent [PS4](3-) anions of 2-4 have been assigned in the range 200-650 cm(-1) by comparison of their corresponding far/mid infrared and Raman spectra (lambda(exc) = 488 nm) on account of locally imposed C, symmetry. In the Fourier-transform-Raman spectrum = 1064 nm) of 2-4, very similar well-resolved electronic Raman (ER) transitions from the electronic Nd3+ ground-state to two levels of the I-4(9/2) ground manifold and to the six levels of the I-4(11/2) manifold have been determined. Resonant Raman excitation via a B-term mechanism involving the I-4(15/2) and F-4(3/2) intermediate states may account for the significant intensity enhancement of the ER transitions with respect to the symmetric P-S stretching vibration nu(1). Broad absorptions in the UV/vis/NIR diffuse reflectance spectrum at 293 K in the range 5000-25000 cm(-1) of 2-4 are attribued to spin-allowed excited quartet states [(4)(I < F < S < G < D)] and spin-forbidden doublet states [2(H < G < K < D < P)] of Nd3+. A luminescense spectrum of 3 obtained at 15 K by excitation with 454.5 nm shows multiplets of narrow lines that reproduce the Nd3+ absorptions. Sharp and intense luminescence lines are produced instead by excitation with 514.5 nm. Lines at 18681 ((4)G(7/2)), 16692 ((4)G(5/2)), 14489 (F-4(9/2)), and 13186 cm(-1) (4F(7/2)) coincide with the corresponding absorptions. Hypersensitive (4)G(5/2) is split by 42 cm(-1). The most intense multiplet at about 16500 cm(-1) is assigned to the transition from (4)G(5/2) to the Stark levels of the ground manifold I-4(9/2)