Crystal and electronic structure of LaAlSi2

LaAlSi2 (a = 4.196(2), c = 11.437(7) Angstrom; P (3) over bar ml; Z = 2) wa s synthesized by arc-melting of preheated mixtures of the elements. The com pound was investigated by means of X-ray methods and by neutron diffraction . The crystal structure can be described as a stacking variant of two diffe rent segments. The first one corresponds to the CaAl2Si2 structure type (La Al2Si2), the second one with the AlB2 structure type (LaSi2). The segments are stacked along [001]. The electronic structure of the compound is discus sed on the basis of LMTO band structure calculations.