Sorting a list alphabetic then numeric

Scenario
I have a list I’m getting back where I have a mixture of letters and numbers as strings. I need the list to be sorted so it’s alphabetic first THEN numeric.

# Sample data

[
    {"1",[]},
    {"A",[]},
    {"B",[]},
    {"C",[]},
    {"D",[]},
    {"E",[]},
    {"F",[]},
    {"3",[]},
    {"4",[]},
    {"5",[]},
    {"6",[]}
]

# But I want this as the final result

[
  {"A", []},
  {"B", []},
  {"C", []},
  {"D", []},
  {"E", []},
  {"F", []},
  {"1", []},
  {"3", []},
  {"4", []}
]

My solution works
This is what I came up with and it seems to work

defmodule Foo do

  @list [
    {"1",[]},
    {"A",[]},
    {"B",[]},
    {"C",[]},
    {"D",[]},
    {"E",[]},
    {"F",[]},
    {"3",[]},
    {"4",[]},
    {"5",[]},
    {"6",[]}
  ]

  def list do
    @list
  end

  def sort_alpha_then_numeric(list) do

    numbers_alpabetic_list =
      Enum.split_with(list, fn item ->
        {key, _value} = item
      case Integer.parse(key) do
        {_, ""} -> true
        :error -> false
      end
    end)

    {number_list, alpha_list} = numbers_alpabetic_list

    # We now switch it so that the order is alpabetic then numeric
    List.flatten(alpha_list, number_list)

  end
end

So if I try this out

Foo.sort_alpha_then_numeric Foo.list
# returns
[
  {"A", []},
  {"B", []},
  {"C", []},
  {"D", []},
  {"E", []},
  {"F", []},
  {"1", []},
  {"3", []},
  {"4", []}
]

Question
It works, but would like to know if my approach can be improved and learn something about sorting. Thanks.