Creating a company specific portfolio

Hey all,

I am trying to get a job at a specific company and i wanted to create a portfolio ( 3d props ) which is suited for the games that they have published. I was wondering if i'm allowed to use the concept art that the artists have published on their portfolios for my 3d models? In addition, is it expected of me to contact the artists and ask their permission or are people generally okay with that if i reference that i created my models based on their concepts?

Thanks in advance and sorry if im asking at the wrong place.