Layered <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>CrG</mml:mi> <mml:msub> <mml:mi mathvariant="normal">e</mml:mi> <mml:mrow> <mml:mn>1</mml:mn> <mml:mo>−</mml:mo> <mml:mi>x</mml:mi> </mml:mrow> </mml:msub> <mml:mi m

We report the synthesis and properties of a new layered material, CrGe1-xSe3+y. The crystal structure was determined by using single crystal x-ray diffraction and transmission electron microscopy. CrGe1-xSe3+y crystallizes with a space group R-3m, featuring a double Kagome layer of chromium atoms, sandwiched between disordered Ge-Se layers. This compound displays antiferromagnetic order below 50 K, unlike the ferromagnetic behavior in CrGeTe3. Chromium displays an effective moment of ~3.9 μB/Cr, consistent with Cr3+ oxidation. The presence of this phase limits the possibility of a ferromagnetic CrGeSe3 analogous to CrGeTe3.