The file of the instances has been uploaded on Mendeley data with the name of 'Quadratic minimum spanning tree problem'. https://data.mendeley.com/datasets/cmnh9xc6wb/1
As well as google drive. https://drive.google.com/file/d/14k1Moxpdx35aJR6KAwUWREOf0m7EwOFY/view
Kindly provided by Hao Jin-kao and Fu Zhang-hua.