I downloaded Ubuntu mate from [Ubuntu-Mate Website][1] . I am unable to extract the .xz file in my mac. On extracting file, it generates .cpgz file. 

Please help me to extract the .img file and boot on a memory card.

Thanks


  [1]: https://ubuntu-mate.org/raspberry-pi/ubuntu-mate-16.04.2-desktop-armhf-raspberry-pi.img.xz