For make your site better in SEO you need to add your sitemap.xml to robots.txt file
Please see following step below
- Login to Google Webmaster Tools.
- Click ‘Go to the old version’
- Go to ‘Crawl -> robots.txt tester’
- Add this line for each sitemap to robot.txt ‘Sitemap: http://www.domain.com/sitemap-products.xml’
- Submit new robot.txt to your website by follow step as same as Google Webmaster Tools provide