Synchrotron X-ray diffraction study of 112-type Ca1−xLaxFeAs2

• Synchrotron X-ray diffraction structural studies of Ca1−xLaxFeAs2 are presented.
• Crystal twins are found in Ca1−xLaxFeAs2 with nominal compositions of x = 0.25.
• Contribution of sp hybridization for arsenic zigzag chains are discussed.
• Possible structures of novel 112-type iron arsenides are discussed.

Synchrotron X-ray diffraction studies of Ca1−xLaxFeAs2 with monovalent arsenic zigzag chain layers are presented. While the crystal twins appear in all samples for the nominal composition of x = 0.25, we successfully obtained the samples without crystal twins for the nominal composition of x = 0.17. We present the structural parameters obtained using the synchrotron X-ray diffraction data and physical properties for the samples with x = 0.17. We further discuss the tactics for exploring novel 112-type iron arsenides without arsenic zigzag chains.