Need help on DAX

 Check that the Material has no false value in its group.

Output =
NOT (
    FALSE
        IN CALCULATETABLE (
            VALUES ( Materials[Check] ),
            ALLEXCEPT ( Materials, Materials[Material] )
        )
)

Slightly less intuitive but simpler:

Output =
CALCULATE (
    SELECTEDVALUE ( Materials[Check] ),
    ALLEXCEPT ( Materials, Materials[Material] )
)

Yes, the second one will return blanks when multiple values are present. These get coerced into FALSE values if the column type is a logical boolean.

To work with "Yes" / "No", I think you could just add an argument to SELECTVALUE for what to return instead of blank when there are multiple values. That is, SELECTEDVALUE ( Materials[Check], "No" ).