Distortion and charge density wave in the Ga square net coupled to the site occupancy wave in YCo0.88Ga3Ge.

YCo 0.88Ga 3Ge has an incommensurately modulated structure that was solved with (3 + 1)D superspace techniques. YCo 0.88Ga 3Ge crystallizes in the orthorhombic superspace group Immm(alpha00)00 s with unit cell constants of a = 4.1639(4), b = 4.1639(4), c = 23.541(2) A and a modulation vector of q = 0.3200(4) a* at 293 K. The incommensurate modulation, which creates a very large supercell ( approximately 25 fold), arises from a charge density wave (CDW) in the square net of Ga atoms that is coupled with a site occupancy wave (SOW) of Co atoms. The distorted Ga net features polygallide ribbons, chains, as well as single atoms. Temperature dependent crystallographic studies of the structure from 100-500 K indicate that the CDW is "locked in". Electrical conductivity and thermopower measurements in the temperature range of 300-500 K show that YCo 0.88Ga 3Ge is a poor metal.