Tetragonal UT2Si2 (T: transition metal) compounds are intensively studied for their interesting properties such as the hidden order and local-moment antiferromagnetic orders with commensurate and incommensurate propagation vectors, and their coexistence with itinerant heavy-fermion states and/or superconductivity. UAu2Si2 has shown puzzling low-temperature properties inconsistent among reported studies. Recently, we succeeded in growing single-crystalline samples of UAu2Si2 for the first time, and obtained a reliable set of experimental data of its thermal, magnetic, and transport properties.The neutron Laue diffraction on a UAu2Si2 single crystal revealed the propagation vectors of magnetic structure, k = (±⅔, 0, 0) and (0, ±⅔, 0). This result is well in agreement with our 29Si-NMR experiment on powder sample, which suggests the conic magnetic structure with ferromagnetic component along the c-axis and antiferromagnetic component confined within the tetragonal basal plane. In order to confirm this scenario and identify the magnetic structure of UAu2Si2, we intend to perform the single crystal neutron diffraction experiment employing D10 four-circle diffractometer.