Spontaneous Gap Opening and Potential Excitonic States in an Ideal Dirac Semimetal Ta2Pd3Te5 Peng Zhang ,1,2,*,?Yuyang Dong,3,*Dayu Yan,4,5,*Bei Jiang,4,5,*Tao Yang,1Jun Li,4Zhaopeng Guo,4,5Yong Huang,1 Haobo ,6Qing Li,1Yupeng Li,4Kifu Kurokawa,3Rui Wang,1,2Yuefeng Nie,6Makoto Hashimoto,7Donghui Lu,7 Wen-He Jiao,8Jie Shen,4Tian Qian,4,5Zhijun Wang ,4,5Youguo Shi,4,5and Takeshi Kondo3,9,? 1School of Physics and National Laboratory of Solid State Microstructures, Nanjing University, Nanjing, China...