Both member-functions should have different template parameter (following will work ok)
template <class T>
class test {
public:
template<typename U>
typename std::enable_if<std::is_atomic<U>::value, bool>::type
foo(U t) { return true; }
template<typename U>
typename std::enable_if<tmp::is_sequence<U>::value, bool>::type
foo(U t) { return false; }
};