It works, but does not scale yet.

specs/Qowaiv.Specs/Financial/Amount_specs.cs

@@ -59,3 +59,13 @@ public void to_divide_amount_by_amount_as_decimal()
         }
     }
 }
+
+public class Supports_try_format
+{
+    [Test]
+    public void On_interpolated_strings()
+    {
+        FormattableString.Invariant($"{Svo.Amount}").Should().Be("42.17");
+    }
+
+}

src/Qowaiv/Financial/Amount.cs

@@ -375,19 +375,6 @@ namespace Qowaiv.Financial;
     [DebuggerBrowsable(DebuggerBrowsableState.Never)]
     private string DebuggerDisplay => this.DebuggerDisplay("¤{0:0.00########}");
 
-    /// <summary>Returns a formatted <see cref="string"/> that represents the current </summary>
-    /// <param name="format">
-    /// The format that describes the formatting.
-    /// </param>
-    /// <param name="formatProvider">
-    /// The format provider.
-    /// </param>
-    [Pure]
-    public string ToString(string? format, IFormatProvider? formatProvider) 
-        => StringFormatter.TryApplyCustomFormatter(format, this, formatProvider, out string formatted)
-        ? formatted
-        : m_Value.ToString(format, Money.GetNumberFormatInfo(formatProvider));
-
     /// <summary>Gets an XML string representation of the amount.</summary>
     [Pure]
     private string ToXmlString() => ToString(CultureInfo.InvariantCulture);

src/Qowaiv/Financial/Amount.experimental.cs

@@ -0,0 +1,47 @@
+namespace Qowaiv.Financial;
+
+
+public partial struct Amount
+#if NET6_0_OR_GREATER
+    : ISpanFormattable
+#endif
+{
+
+#if NET6_0_OR_GREATER
+
+    [Pure]
+    public string ToString(string? format, IFormatProvider? formatProvider)
+    {
+        var span = new Span<char>(new char[128]);
+        ((ISpanFormattable)this).TryFormat(span, out var size, format, formatProvider);
+        return span[..size].ToString();
+    }
+
+    /// <inheritdoc />
+    bool ISpanFormattable.TryFormat(Span<char> destination, out int charsWritten, ReadOnlySpan<char> format, IFormatProvider? provider)
+    {
+        if (StringFormatter.TryApplyCustomFormatter(format.ToString(), this, provider, out string formatted))
+        {
+            formatted.CopyTo(destination);
+            charsWritten = formatted.Length;
+            return true;
+        }
+        else return m_Value.TryFormat(destination, out charsWritten, format, Money.GetNumberFormatInfo(provider));
+    }
+#else
+
+    /// <summary>Returns a formatted <see cref="string"/> that represents the current </summary>
+    /// <param name="format">
+    /// The format that describes the formatting.
+    /// </param>
+    /// <param name="formatProvider">
+    /// The format provider.
+    /// </param>
+    [Pure]
+    public string ToString(string? format, IFormatProvider? formatProvider)
+        => StringFormatter.TryApplyCustomFormatter(format, this, formatProvider, out string formatted)
+        ? formatted
+        : m_Value.ToString(format, Money.GetNumberFormatInfo(formatProvider));
+
+#endif
+}