"material" has different meanings, one of which is "cloth used for making clothes, curtains, etc." according to Oxford dictionary There is an example in which material is plural
The military uses synthetic materials for clothing because they're more durable than cotton.
I wonder why they have to use materials in this case. Normally, if a word can be both countable and uncountable and its singular form is rarely used, the dictionary will probably note that "usually ....(that word in plural form), and either plural form or uncountable form will mean the same, but in the entry for material they don't. Therefore I suppose "a material" can be used. It's obvious that we can't count cloth so why its synonym, material, is countable? I can't come up with any cases where material can be in singular form.