How can I remove the sidebar from category homepage only ? but not from category's posts

Hi,

I put a part of my project (with fake/test content only, work in progress style) on a development online domain server: http://www.madig.biz

On this site, I get 6 categories “assurance, banque, credit, etc” put in the top left menu. I intend to create 6 sidebars, one different for each category.

I have customized the category homepages (see examples http://www.madig.biz/assurance and http://www.madig.biz/credit ) to add specific text and call to action with images only on category first page. To do so I use a standard “php if is_category()” code.

I don’t want sidebar on category main page, but i want sidebar on category posts from the concerned category. I only manage to get the category sidebar to "category homepage" + all category posts, but not only on posts.

So the need is to remove sidebar from category homepages.

Could you please explain me how can I do to fix that issue?

Thanks for you help, very appreciated.

Thibault