Given a positive integer $k$. Find the condition of positive integer $m$ over $k$ such that there exists only one positive integer $n$ satisfying $$n^m | 5^{n^k} + 1,$$
**
   Given a positive integer \( k \), we need to find the condition on a positive integer \( m \) such that there exists only one positive integer \( n \) satisfying \( n^m \mid 5^{n^k} + 1 \). 

   Clearly, \( n = 1 \) is a solution because \( 1^m = 1 \) divides any integer, including \( 5^{1^k} + 1 = 6 \).

2. **Exclusion of \( n = 3 \):**
   We need to ensure that \( n = 3 \) is not a solution. If \( n = 3 \), then \( 3^m \mid 5^{3^k} + 1 \). We need to show that this does not hold for \( m \geq 3 \).

3. **Considering \( n \) is Even:**
   If \( n \) is even, then \( n \geq 2 \). Consider the expression modulo 4:
   \[
   5^{n^k} + 1 \equiv 1 + 1 \equiv 2 \pmod{4}
   \]
   Since \( n^m \) is even, it must be at least 2, which cannot divide 2. Hence, \( n \) cannot be even.

4. **Considering \( n = 3 \):**
   Using the LTE (Lifting The Exponent) lemma, if \( n = 3 \), we need to check the divisibility condition:
   \[
   3^m \mid 5^{3^k} + 1
   \]
   For \( m \leq 1 + k \), this would be a contradiction. Therefore, \( m \geq k + 2 \).

5. **Minimal Prime Divisor Argument:**
   Let \( q \) be the minimal prime divisor of \( n \). Clearly, \( q \geq 7 \) because smaller primes would lead to contradictions as shown above. We have:
   \[
   5^{2n^k} \equiv 1 \pmod{q}
   \]
   and
   \[
   5^{q-1} \equiv 1 \pmod{q}
   \]
   This implies that the order of 5 modulo \( q \) must divide both \( 2n^k \) and \( q-1 \). Since \( q \geq 7 \), this leads to a contradiction unless \( n = 1 \).

6. **Conclusion:**
   Therefore, the condition for \( m \) is \( k + 2 \leq m \). This ensures that \( n = 1 \) is the only solution.

The final answer is \( \boxed{ k + 2 \leq m } \)