File Exist with same name error. Error message: The file 'Assets\Material\HiddenPreview.mat' already exists.

[codeswapping]

Why program is trying to create the file with same name as existing one? I tried to avoid it by using File.Exist() check but I found that, it is not generating other folder than assets. Also script files are missing. I am not sure this issue is related to file already exists error but I am facing such issues.