I create my signer wallet as follows:

const seed = bip39.mnemonicToSeedSync(WALLET_MNEMONIC, WALLET_PASSWORD);
const privateKeyBuffer = bip32
    .fromSeed(seed)
    .derivePath(`m/44'/434'/0'/0/0`).privateKey; 
const keyring = new Keyring({ss58Format: 2});
return keyring.addFromAddress('0x'+privateKeyBuffer.toString("hex"));

and I try to transfer KSM from that account into another one:

const unsub = await api.tx.balances
    .transfer(recipientAddress, amount)
    .signAndSend(signerWallet, (result) => {
        console.log(`Current status is ${result.status}`);
        if (result.status.isInBlock) {
            console.log(`Transaction included at blockHash ${result.status.asInBlock}`);
        } else if (result.status.isFinalized) {
            console.log(`Transaction finalized at blockHash ${result.status.asFinalized}`);
            unsub();
        }
    });

However I get that error:

Cannot sign with a locked key pair

What is the problem with my code?