Charge density wave formation and physical properties of $R_{2}$Te$_{5}$ ($R$=Nd, Gd) compounds*

$R_{2}$Te$_{5}$ ($R$=Nd, Gd) has a layered tetragonal structure based on alternating single and double square planar Te sheets separated by corrugated $R$Te layers, and has a quasi-two dimensional electronic structure. The material shares important physical properties with other two single and double Te layer variants, $R$Te$_{2}$ and $R$Te$_{3}$ (R=La~Yb), including a charge density wave (CDW) instability. Using a binary self-flux method, we have grown high-quality single crystals of Gd$_{2}$Te$_{5}$ and Nd$_{2}$Te$_{5}$ compounds and have characterized their structural, thermodynamic and transport properties. Our measurements reveal, for the first time, the charge density wave in this material. We will discuss the properties and origin of the CDW, and the relation to the better known $R$Te$_{2}$ and $R$Te$_{3}$ compounds.